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Discussion Starter #1
Well the horn on the Toyota I just got is not working. I did a search on this issue and tested all likely faults, e.g., relay (changed it), fuses (all tested good), horn itself (wired directly to battery and it blared). When I hit the horn button on the center of the steering wheel, which is basically the airbag, I can hear the relay clicking and when I replaced the relay, I still get clicking but no horn sound. Like I said, I proved the horn works as well as the fuses. I'm starting to worry that it might be the clock spring or worn contact in the steering wheel behind the airbag? I was able to successfully change the clock spring to my XL7 before because the horn didn't work and my airbag light was on, but I don't have an airbag light lit on the Toyota. I do hear the relay clicking so isn't the contacts in the steering wheel making some sort of contact if it's closing the relay? I'm a little bit at a loss, does anyone else have a clue?
 

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if the relay is clicking, then the horn switch is working on the column, its that simple.
Your issue is in the "high power" side. Checked the fuse box under the hood for the 15A "horn" fuse? yep, theres usually 2 in Toymotas, one inside the cabin that does the "low power" relay side and another in the engine bay.
Check for broken wires between the fuse box and the horn itself, and measure volts at the horn. theres 2 possible wiring types on the Toyotas.

From memory these should have one side of the horn grounded (multimeter to ground, one wire should have 0 ohms, other wire should go to +12 when button is pressed.
If you have one side at +12 and nothing on the other side in terms of continuity, then its the "ground" version where the relay is in the ground side and closes the wire to ground to make the horn work.
I think you have either no power to the horn, or a bad ground. its just a pain, but checking the wiring back might be the only way.

Check for volts, or continuity depending on system at the relay contact terminals. jump the contact terminals with a paper clip, if the horn sounds, then the relay is faulty, if it doesn't start looking from contact to horn, and other contact terminal to ground, or +12 depending on whether its a + switched or a ground switched system. Toyota used both!!!

When you do find it, you will swear, curse then feel really satisfied for finding it.

oh, there may be a "high power" horn relay in the fuse box under the hood, that ones driven by the one on the fuse panel in the cabin, there again, some toyotas have them, some don't
 

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Discussion Starter #3
if the relay is clicking, then the horn switch is working on the column, its that simple.
Your issue is in the "high power" side. Checked the fuse box under the hood for the 15A "horn" fuse? yep, theres usually 2 in Toymotas, one inside the cabin that does the "low power" relay side and another in the engine bay.
Check for broken wires between the fuse box and the horn itself, and measure volts at the horn. theres 2 possible wiring types on the Toyotas.

From memory these should have one side of the horn grounded (multimeter to ground, one wire should have 0 ohms, other wire should go to +12 when button is pressed.
If you have one side at +12 and nothing on the other side in terms of continuity, then its the "ground" version where the relay is in the ground side and closes the wire to ground to make the horn work.
I think you have either no power to the horn, or a bad ground. its just a pain, but checking the wiring back might be the only way.

Check for volts, or continuity depending on system at the relay contact terminals. jump the contact terminals with a paper clip, if the horn sounds, then the relay is faulty, if it doesn't start looking from contact to horn, and other contact terminal to ground, or +12 depending on whether its a + switched or a ground switched system. Toyota used both!!!

When you do find it, you will swear, curse then feel really satisfied for finding it.

oh, there may be a "high power" horn relay in the fuse box under the hood, that ones driven by the one on the fuse panel in the cabin, there again, some toyotas have them, some don't
Thanks for the tips. Well, I checked all three fuse locations for my 94 Celica, one on interior driver side, one on interior passenger side, and one underneath the hood with all the relays. I only saw one 7.5A fuse for the horn under the hood, near a horn relay, as the fuse box diagrams showed. I verified both the fuse and relay were good, and in fact replaced the relay.

So I took a circuit tester to the single wire lead at the horn, grounded the other end of the tester, then pressed the horn button and got no light at the tester, which means no power is getting the the horn.

I traced the wiring backwards visually with a flashlight as far as I could and it's all tightly wire wrapped in plastic with all the other wiring, so it's hard for me to believe there's a break somewhere in the wiring.

I know you said the fact the relay is clicking means the contacts at the steering column is ok, but do you think something at the steering column is not fully closing the horn circuit even though the relay is clicking to supply power to the rest of the horn circuit? I plan to remove the airbag (yeah I know) like I did when I replaced the clock spring in my XL7 to see if there's a contact underneath that's not making contact. I know when I replaced the clock spring to my XL7 both the airbag light was lit and the horn wasn't working, but in the Toyota's case there's no airbag light on, so is it possible to still have a bad clock spring not closing the circuit for the horn, with the airbag light not lit?
 

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Thanks for the tips. Well, I checked all three fuse locations for my 94 Celica, one on interior driver side, one on interior passenger side, and one underneath the hood with all the relays. I only saw one 7.5A fuse for the horn under the hood, near a horn relay, as the fuse box diagrams showed. I verified both the fuse and relay were good, and in fact replaced the relay.

So I took a circuit tester to the single wire lead at the horn, grounded the other end of the tester, then pressed the horn button and got no light at the tester, which means no power is getting the the horn.

I traced the wiring backwards visually with a flashlight as far as I could and it's all tightly wire wrapped in plastic with all the other wiring, so it's hard for me to believe there's a break somewhere in the wiring.

I know you said the fact the relay is clicking means the contacts at the steering column is ok, but do you think something at the steering column is not fully closing the horn circuit even though the relay is clicking to supply power to the rest of the horn circuit? I plan to remove the airbag (yeah I know) like I did when I replaced the clock spring in my XL7 to see if there's a contact underneath that's not making contact. I know when I replaced the clock spring to my XL7 both the airbag light was lit and the horn wasn't working, but in the Toyota's case there's no airbag light on, so is it possible to still have a bad clock spring not closing the circuit for the horn, with the airbag light not lit?
If you are pressing the horn button and the relay under the hood is clicking, then that parts fine. What happens if you short across the relay contacts with the relay out, as in simulate the relay closing, does the horn sound? if not, start chasing wires. Does the relay actually have 12V at the contact terminal? one side should, other side should have continuity to the horn. I'm betting the wire to the horn has a break in it somewhere. Just because its all taped up doesn't mean there isn't a break somewhere.

Before you pull things apart (which won't get you anywhere i feel) check continuity from the relay socket to the horn, i bet its open circuit.
 

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Discussion Starter #5
If you are pressing the horn button and the relay under the hood is clicking, then that parts fine. What happens if you short across the relay contacts with the relay out, as in simulate the relay closing, does the horn sound? if not, start chasing wires. Does the relay actually have 12V at the contact terminal? one side should, other side should have continuity to the horn. I'm betting the wire to the horn has a break in it somewhere. Just because its all taped up doesn't mean there isn't a break somewhere.

Before you pull things apart (which won't get you anywhere i feel) check continuity from the relay socket to the horn, i bet its open circuit.
I did what you advised and jumpered the relay contacts. The contacts are configured this way: two are vertical next to each other side by side (I assume those are 1 and 2 on the relay), and one horizontal contact above the other two (I assume this is 3), as the relay itself is labeled with a tiny schematic that says you have to close 1 and 2 to trip 3. I'm assuming shorting the two vertical contacts will do this, and when I did, it did not get the horn to blow. For kicks I just shorted any one of the three to each other, hopefully didn't screw anything up in the process but according to the schematic if I did try to short the wrong two contacts, it would leave the correct 1 and 2 open anyways. But regardless of what I shorted, there was no horn sound.

Can I use my continuity tester, or better yet a voltmeter to check if there's 12v going to one of the contact terminals? The fact that the relay is clicking, wouldn't there be? I guess it doesn't hurt to check. But yeah I'm beginning to think it's the wiring from the relay box to the horn. I wish there was a way where I can just bypass that wiring and somehow rig new wiring from the relay box to the horn, or if I can at least find the right wire coming from the horn relay junction to tap into and run straight to the horn. I do see a little kink coming from where the horn wire is exiting the wiring harness and runs to the connector to the horn, I'll probably slice the sheath over that open to see if there's a break there, for starters.

Thanks again for your help, what a bothersome conundrum for such a simple circuit. :confused:
 

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ok, 3 terminal relay?

you "should" have a scenario looking at the schematic where there is a coil that pulls in a contact. simple electrics, 12V across coil makes it pull the contact in. Look at the contact on the diagram and work out what pin is common to coil and contact, that should have +12 on it and therefore, +12 on the other "contact" pin when the relay is energised.
The coil pin in common with the contact is +12, the other side of the coil goes to ground when you press the horn button (this makes it go "click" ) and the +12 should appear on the other contact pin when the relay is energised.

You should now be able to work out what hole goes where and start tracing things, continuity on the pin to the horn button should show 0 ohms button pressed, high ohms button released. contact to horn should show some ohms if the wire to the horn, and the ground connection at the horn is any good. use volts scale as required to determine which pin has volts and go from there.

as a silly question, does the horn have 1 terminal on it or 2?
 

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Discussion Starter #7
ok, 3 terminal relay?

you "should" have a scenario looking at the schematic where there is a coil that pulls in a contact. simple electrics, 12V across coil makes it pull the contact in. Look at the contact on the diagram and work out what pin is common to coil and contact, that should have +12 on it and therefore, +12 on the other "contact" pin when the relay is energised.
The coil pin in common with the contact is +12, the other side of the coil goes to ground when you press the horn button (this makes it go "click" ) and the +12 should appear on the other contact pin when the relay is energised.

You should now be able to work out what hole goes where and start tracing things, continuity on the pin to the horn button should show 0 ohms button pressed, high ohms button released. contact to horn should show some ohms if the wire to the horn, and the ground connection at the horn is any good. use volts scale as required to determine which pin has volts and go from there.

as a silly question, does the horn have 1 terminal on it or 2?
Not a silly question, as I always appreciate the assistance. The original horn has 1 terminal on it, so it's a one wire horn. I was trying to embed the image of the schematic on the relay from my Photobucket site, but Photobucket is being uncooperative so I hope you don't mind I attached the pics instead. If you take a look at it, it looks like #3 is the point where 12v should be applied? So when 12v is applied across 3, 1 and 2 closes and delivers 12v to horn?

I also attached a pic of the inside of the relay, am I guessing right that 3 is the one horizontal contact separate from the other two vertical contacts (1 and 2)? So in the relay bay, should I be jumping contacts for 1 and 2 for the short? Like my previous post, I wasn't getting any horn sound shorting those, if I chose the correct points to short.

I wish they were numbered like some other relays but as you can see it's not so i'm just guessing.
 

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Not a silly question, as I always appreciate the assistance. The original horn has 1 terminal on it, so it's a one wire horn. I was trying to embed the image of the schematic on the relay from my Photobucket site, but Photobucket is being uncooperative so I hope you don't mind I attached the pics instead. If you take a look at it, it looks like #3 is the point where 12v should be applied? So when 12v is applied across 3, 1 and 2 closes and delivers 12v to horn?

I also attached a pic of the inside of the relay, am I guessing right that 3 is the one horizontal contact separate from the other two vertical contacts (1 and 2)? So in the relay bay, should I be jumping contacts for 1 and 2 for the short? Like my previous post, I wasn't getting any horn sound shorting those, if I chose the correct points to short.

I wish they were numbered like some other relays but as you can see it's not so i'm just guessing.
ok, looking at the pic, and IF toyota follow usual tricks on your model,
#2 should be live 12V all the time fed from that 7.5A fuse you found.
3 should go to ground when you press the horn button, and 12V should appear on terminal 1 when button is pressed. (2 closes onto 1 when relay pulls in, isn't electrical stuff fun) 3 to 2 is the relay coil, so that needs 12V across it to make it work, so you can figure out why terminal 3 goes to ground via the horn button.
so.... jumping 1 and 2 should make the horn sound, if you have no 12V at terminal 2 (the common terminal) then start looking as to why, one side of the 7.5A fuse should be live all the time, the other side should go to terminal 2 of the relay.
if theres 12V at 2, and jumping to 1 doesn't make the horn sound, then theres a break in the wiring somewhere between he relay and the horn.
As a silly double check, leave the horn in place, run a wire from +12 on the battery to the horn terminal (take the car wire off it first) it is a 1 wire horn? i think you told me it was earlier, and see if the horn sounds, this will at least prove the horn is ok when fitted and has a good earth. If it doesn't work in place, then check continuity from horn frame to batt -Ve.
Continuity (low ohms, like 1 ohm) between horn wire and terminal 1 indicates car wiring is ok and then you are looking for a bad ground or no volts depending of what side of the circuit you are chasing.

To work out which terminal is which, find the one with 12V on it, then use continuity to find which one of the other 2 goes to ground when the horn button is pressed, use the "diode" or beep range, then you can make beep noises using the horn button and drive yourself nuts, by elimination, the last terminal should go to the horn.

let me know what you find.
 

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Discussion Starter #9 (Edited)
Ok, back to trying to figuring this puzzling horn issue out. See some of my results below:

ok, looking at the pic, and IF toyota follow usual tricks on your model,
#2 should be live 12V all the time fed from that 7.5A fuse you found. I verified this by removing the relay and putting my circuit tester on what is interpreted as #2 on the schematic, and I have 12V there on #2, as well as 12V on one end of the 7.5A fuse.
3 should go to ground when you press the horn button, and 12V should appear on terminal 1 when button is pressed. (2 closes onto 1 when relay pulls in, isn't electrical stuff fun) 3 to 2 is the relay coil, so that needs 12V across it to make it work, so you can figure out why terminal 3 goes to ground via the horn button.
so.... jumping 1 and 2 should make the horn sound, if you have no 12V at terminal 2 (the common terminal) then start looking as to why, one side of the 7.5A fuse should be live all the time (yes, as I mentioned earlier I verified that one side of the 7.5A fuse is live all the time), the other side should go to terminal 2 of the relay.

if theres 12V at 2, and jumping to 1 doesn't make the horn sound, then theres a break in the wiring somewhere between he relay and the horn.This is pretty much what I'm suspecting, see rest of my notes below.

As a silly double check, leave the horn in place, run a wire from +12 on the battery to the horn terminal (take the car wire off it first) it is a 1 wire horn? i think you told me it was earlier, and see if the horn sounds, this will at least prove the horn is ok when fitted and has a good earth. If it doesn't work in place, then check continuity from horn frame to batt -Ve. Ran this test and yes, horn sounded while in place, so that proves horn has good ground.

Continuity (low ohms, like 1 ohm) between horn wire and terminal 1 indicates car wiring is ok and then you are looking for a bad ground or no volts depending of what side of the circuit you are chasing.

To work out which terminal is which, find the one with 12V on it, then use continuity to find which one of the other 2 goes to ground when the horn button is pressed, use the "diode" or beep range, then you can make beep noises using the horn button and drive yourself nuts, by elimination, the last terminal should go to the horn. I pretty much know what #2 is since it's always 12V there as determined previously above, but the test you're suggesting here, is this with the relay removed or inserted? Because with the relay removed, I put my circuit tester on either "dead" slots (1 or 3, which have no voltage, and I'm not getting any light on the tester, as shouldn't one of them get lit with getting power from 2 when I press the airbag at the steering wheel, and the other going to ground?)

This is basically where I'm at, as there's 12V at #2 and jumping it to #1 didn't make it sound. I also cut the horn wire a few inches from the connector and used alligator clips from the one end of the horn wire to the horn itself, ruling out the connector, and still no sound. I stripped the sleeve off the horn wire where I thought there was a kink, but no kink or break at that spot. The rest of the wire then goes into the harness, which runs underneath the top cross member just in front of the radiator and disappears into underneath the fuse and relay box in the engine bay. I have no idea what to check for now unless I just undo the entire wiring harness but why would I do that for a single horn wire? Is there a way where I can run a wire from either one of the relay terminals or 7.5A fuse terminals (like from the relay slot for #1, or the slot that is not live for the 7.5A fuse) straight to the horn, and jerry rig it that way? Which one is in front of the other, the fuse or the relay, before it gets to the horn?

let me know what you find.
 

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To work out which terminal is which, find the one with 12V on it, then use continuity to find which one of the other 2 goes to ground when the horn button is pressed, use the "diode" or beep range, then you can make beep noises using the horn button and drive yourself nuts, by elimination, the last terminal should go to the horn.
I pretty much know what #2 is since it's always 12V there as determined previously above, but the test you're suggesting here, is this with the relay removed or inserted?
removed

Because with the relay removed, I put my circuit tester on either "dead" slots (1 or 3, which have no voltage, and I'm not getting any light on the tester, as shouldn't one of them get lit with getting power from 2 when I press the airbag at the steering wheel, and the other going to ground?)
no, you need to be on continuity as the horn button takes one of these terminals to ground, not to +12, test light will not light, if you connect one side of the test light to +12 and the other to the terminal, it should light if you press the horn button (got to think reversed now, you are chasing something switching to ground now)

This is basically where I'm at, as there's 12V at #2 and jumping it to #1 didn't make it sound.
ok, you have whats known as an "air gap" in the wiring between relay and horn. now we are getting somewhere.


ok, with the relay out, use meter on continuity range and one of the "non live" terminals should short to ground when you press the horn button. the one that doesn't is the one going to the horn, and that should be terminal 1 on the relay. 2 is live at 12V, 3 will go to ground when you press the horn button.

I also cut the horn wire a few inches from the connector and used alligator clips from the one end of the horn wire to the horn itself, ruling out the connector, and still no sound.
wait a bit, next test, jump the horn side of the cut wire to +12 and the horn should sound. if it does then the break is between that cut and the relay. if thats the case, follow the loom back to the other side of the cross member, find the wire, cut it, join at the original cut (strip and twist together for now) jump horn side to +12, horn works? break is between there and relay terminal, horn no go, break is in wiring across front of car.
this will now narrow down where in the loom the issue is. Not a nice way of fault finding, but its the easiest way. if youre confused, i've added a hand drawn diagram to explain everything. Big black square is the battery, the wire from the horn to the battery is ground, obviously this is the chassis on the car in your case and the line is drawn just to show the electrical circuit.

Now can you see why you don't see the light on the horn button side of the relay socket when you press the button? you are trying to make a test light illuminate that will always have 0V across it.

ok, ok, i missed the fuse between the battery and terminal 2 in the diagram. sorry.
 

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Thank you, thank you! I appreciate your ongoing help despite me not having resolved this yet, but i think you're helping me get closer. Let me throw another loop into this, as I was tracing the loom back to see where it meets the relay/fuse box, I looked down toward the bottom of the radiator and guess what I saw? Another horn! In fact, it may be the original horn location, and I'm guessing the other one towards the top of cross member which I've been working on, which I thought was kind of in a weird location in the first place, is an attempt to install another horn rather than fix the one that I just discovered at the lower front, just to the right of the radiator.

So let me review for you what I see with the two horns:

The first horn which I though was the only horn, is mounted towards the top cross member, and is only single-wire, grounded to the cross member with the mounting bolt.

The second horn I discovered in the lower part behind the bumper just to the right of the radiator is a two-wire horn, one of the two wires was cut off from the connector. I'm assuming the ground is also through being bolted to the frame next to the radiator.

So I figured this might be it (the second horn), all I need to do is reconnect one of the two cut wires to the horn connector and all's well. Well, just like the other horn, what I did was completely cut the connector (to rule out a bad connector) and just alligator clipped the two wires to the horn, one to the horn contact and the other to ground, pressed the button, still no sound. Damn. I took that second horn and put it across 12V, and it sounded, so I know the horn is good.

Now that i think about it as I'm typing this, for the second horn, why are there two wires going into the one connector? i.e., the two wires are crimped to a single connector and in turn that connector is connected to the single horn contact? That's the only thing I didn't try after I cut the connector, I may just have to simply join the two wires together and ground the original horn (the second horn which I tested good), onto the frame, and see if that does it. Can't wait to try this when I get home, but won't hold my breath. :rolleyes:

I'm totally confused as to why there was that one single wire horn that I was working with at first, but it's only a single wire coming out of the harness at at totally different spot of the harness, opposite of the two-wire conductor coming out of the other end of the harness for the second horn, which is actually closer to the relay/fuse box, just lower on the bumper. I was thinking maybe the previous owner tried to put the more visible horn (the single wire horn near the top), as a replacement, bypass, or in series to the second horn I discovered with two wires, which again I think is truly the original horn, but may have to verify with my colleagues at the Toyota forum as to what the original horn location was. So confused :confused:
 

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either way, you have no power getting to the horns from the relay.......its in that loom section somewhere.
 

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Discussion Starter #13
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no, you need to be on continuity as the horn button takes one of these terminals to ground, not to +12, test light will not light, if you connect one side of the test light to +12 and the other to the terminal, it should light if you press the horn button (got to think reversed now, you are chasing something switching to ground now)


ok, you have whats known as an "air gap" in the wiring between relay and horn. now we are getting somewhere.


ok, with the relay out, use meter on continuity range and one of the "non live" terminals should short to ground when you press the horn button. the one that doesn't is the one going to the horn, and that should be terminal 1 on the relay. 2 is live at 12V, 3 will go to ground when you press the horn button.


wait a bit, next test, jump the horn side of the cut wire to +12 and the horn should sound. if it does then the break is between that cut and the relay. if thats the case, follow the loom back to the other side of the cross member, find the wire, cut it, join at the original cut (strip and twist together for now) jump horn side to +12, horn works? break is between there and relay terminal, horn no go, break is in wiring across front of car.
this will now narrow down where in the loom the issue is. Not a nice way of fault finding, but its the easiest way. if youre confused, i've added a hand drawn diagram to explain everything. Big black square is the battery, the wire from the horn to the battery is ground, obviously this is the chassis on the car in your case and the line is drawn just to show the electrical circuit.

Now can you see why you don't see the light on the horn button side of the relay socket when you press the button? you are trying to make a test light illuminate that will always have 0V across it.

ok, ok, i missed the fuse between the battery and terminal 2 in the diagram. sorry.
I'm following you, and you are very close to helping me isolate where the issue may lie. I searched the wiring diagram for my car (attached below) and it's very close to what you drew for me, but found out that there are indeed two horns in the configuration, which look to be set up in parallel (vs. series), do I have that right?

With the factory schematic, it's now confirmed that it is the green/red wire that is the horn wire, but still dumbfounded why one of the green/red wires is a single wire to one horn, but the other green red wire(s) is actually two wires homing into the second single horn contact. So if I'm interpreting the schematic correctly, pressing the horn pad at the steering wheel supposed to ground (closes or shorts) 12v at terminal 1 and 2, enabling the relay to close at 3, and therefor supply 12v to both horns?

So based on the troubleshooting protocol you gave me above, did I circle in red correctly where the air gap or break may lie?
 

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I'm following you, and you are very close to helping me isolate where the issue may lie. I searched the wiring diagram for my car (attached below) and it's very close to what you drew for me, but found out that there are indeed two horns in the configuration, which look to be set up in parallel (vs. series), do I have that right?
yep!!! spot on, and wow, the dumb kiwi drew it almost like the factory hehehe

With the factory schematic, it's now confirmed that it is the green/red wire that is the horn wire, but still dumbfounded why one of the green/red wires is a single wire to one horn, but the other green red wire(s) is actually two wires homing into the second single horn contact. So if I'm interpreting the schematic correctly, pressing the horn pad at the steering wheel supposed to ground (closes or shorts) 12v at terminal 1 and 2, enabling the relay to close at 3, and therefor supply 12v to both horns?

So based on the troubleshooting protocol you gave me above, did I circle in red correctly where the air gap or break may lie?
yep, the fault is in the bit from the first horn to the relay i'm thinking.

So if I'm interpreting the schematic correctly, pressing the horn pad at the steering wheel supposed to ground (closes or shorts) 12v at terminal 1 and 2, enabling the relay to close at 3, and therefor supply 12v to both horns?
close but not quite, right idea, wrong theory. End result is the same tho.

ok, terminal 2 is "hot" all the time, when terminal 3 goes to ground, current flows thru the relay coil causing it to close the contact and short terminal 1 and 2 together, sending +12 from the fuse, thru the relay contact to the horns, which are wired in parallel so both horns sound together.

The fact one horn has 2 wires at its terminal is merely where they "cut into" the wire to fit that horn, then continued onto the other horn. If neither horn is working, then the fault is between the first horn and the relay.
 

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I'm following you, and you are very close to helping me isolate where the issue may lie. I searched the wiring diagram for my car (attached below) and it's very close to what you drew for me, but found out that there are indeed two horns in the configuration, which look to be set up in parallel (vs. series), do I have that right?
yep!!! spot on, and wow, the dumb kiwi drew it almost like the factory hehehe

With the factory schematic, it's now confirmed that it is the green/red wire that is the horn wire, but still dumbfounded why one of the green/red wires is a single wire to one horn, but the other green red wire(s) is actually two wires homing into the second single horn contact. So if I'm interpreting the schematic correctly, pressing the horn pad at the steering wheel supposed to ground (closes or shorts) 12v at terminal 1 and 2, enabling the relay to close at 3, and therefor supply 12v to both horns?

So based on the troubleshooting protocol you gave me above, did I circle in red correctly where the air gap or break may lie?
yep, the fault is in the bit from the first horn to the relay i'm thinking.

So if I'm interpreting the schematic correctly, pressing the horn pad at the steering wheel supposed to ground (closes or shorts) 12v at terminal 1 and 2, enabling the relay to close at 3, and therefor supply 12v to both horns?
close but not quite, right idea, wrong theory. End result is the same tho.

ok, terminal 2 is "hot" all the time, when terminal 1 goes to ground, current flows thru the relay coil causing it to close the contact and short terminal 1 and 3 together, sending +12 from the fuse, thru the relay contact to the horns, which are wired in parallel so both horns sound together.

The fact one horn has 2 wires at its terminal is merely where they "cut into" the wire to fit that horn, then continued onto the other horn. If neither horn is working, then the fault is between the first horn and the relay.

My numbers are wrong compared to your wiring diagram and I based mine on the relay picture you posted...which makes me wonder....is the relay actually correct?

anyway, you're on the right path
 

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Discussion Starter #16 (Edited)
The fact one horn has 2 wires at its terminal is merely where they "cut into" the wire to fit that horn, then continued onto the other horn. If neither horn is working, then the fault is between the first horn and the relay.

My numbers are wrong compared to your wiring diagram and I based mine on the relay picture you posted...which makes me wonder....is the relay actually correct?

anyway, you're on the right path
With your help, I went on the right path and found Utopia (or should I say Horntopia)! I went from two non-working horns to two working horns (stereo horns?), and problem solved! That second wire at the first horn is just as you described, a path to the second horn. The fault was a combination of the two wires not being joined together at the connector of the first horn (closest to the fuse/relay box), which was corroded because each time I tried to use the connector after re-splicing the two wires back together to the connector, no beep, but when I spliced the two wires to another wire with a clean alligator clip on the other end, which I clipped onto the first horn contact, PLUS I had to create a clean ground point by sanding the paint and corrosion off to bare metal where the horn is bolted onto the frame (there's a big argument in another car forum about whether or not removing the paint off will actually help with grounding, but I'm a believer of it, especially after this exercise), I got music to my ears after all that.

So it was both an open circuit and grounding issue. I temporarily have it alligator clipped but will get a female spade connector for the permanent connection to the horn terminal. One other interesting thing to note, the horn wire is very thin, and when I spliced it to a thicker gauge wire to run to the horn contact, like 14 or 16, I wasn't getting any results, but when I went with 18 gauge wire, then I was getting the beeping. Don't know if that was just coincidence or if the thinner conductor really helped.

As far as the relay drawing, yeah it seems 1 and 3 are inter-switched on the drawing on the relay compared to the factory schematic, but at this point I didn't have a chance to verify it with the continuity test because I was able to isolate the fault at the first horn.

A combination of your tips and the factory schematic a colleague from the Toyota forum referred me to got me there, so a big THANK YOU. Plus I learned a lot in terms of troubleshooting. Probably shouldn't have taken this long but I could not work on it continuously with the stereo replacement project on my other vehicle, but better late than never. I feel a little bit safer to drive the vehicle with an alert device, plus relieved I didn't have to go fiddle with the spiral cable behind the steering wheel.

I'd buy you a cold one but instead I'll have one in your honor. :beer::thumbsup:Thanks again sir!
 

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With your help, I went on the right path and found Utopia (or should I say Horntopia)! I went from two non-working horns to two working horns (stereo horns?), and problem solved! That second wire at the first horn is just as you described, a path to the second horn. The fault was a combination of the two wires not being joined together at the connector of the first horn (closest to the fuse/relay box), which was corroded because each time I tried to use the connector after re-splicing the two wires back together to the connector, no beep, but when I spliced the two wires to another wire with a clean alligator clip on the other end, which I clipped onto the first horn contact, PLUS I had to create a clean ground point by sanding the paint and corrosion off to bare metal where the horn is bolted onto the frame (there's a big argument in another car forum about whether or not removing the paint off will actually help with grounding, but I'm a believer of it, especially after this exercise), I got music to my ears after all that.

So it was both an open circuit and grounding issue. I temporarily have it alligator clipped but will get a female spade connector for the permanent connection to the horn terminal. One other interesting thing to note, the horn wire is very thin, and when I spliced it to a thicker gauge wire to run to the horn contact, like 14 or 16, I wasn't getting any results, but when I went with 18 gauge wire, then I was getting the beeping. Don't know if that was just coincidence or if the thinner conductor really helped.

As far as the relay drawing, yeah it seems 1 and 3 are inter-switched on the drawing on the relay compared to the factory schematic, but at this point I didn't have a chance to verify it with the continuity test because I was able to isolate the fault at the first horn.

A combination of your tips and the factory schematic a colleague from the Toyota forum referred me to got me there, so a big THANK YOU. Plus I learned a lot in terms of troubleshooting. Probably shouldn't have taken this long but I could not work on it continuously with the stereo replacement project on my other vehicle, but better late than never. I feel a little bit safer to drive the vehicle with an alert device, plus relieved I didn't have to go fiddle with the spiral cable behind the steering wheel.

I'd buy you a cold one but instead I'll have one in your honor. :beer::thumbsup:Thanks again sir!
glad you got there, simple fault finding process at the end of it, but you have learned something and thats the main thing.

couple of things in the post you made i'll answer so you can expand your knowledge.

Paint = insulator, surfaces must be clean and metal to metal for a good contact. Rust is also a poor conductor as you have found.

thinner wire? nahh, you had a bad connection. wire gauge is important when it comes to current carrying capacity, bigger wire = less voltage drop

So it was both an open circuit and grounding issue.
and these are the worst of all to find. As my tutor told me 40 years ago, "all faults are an open circuit, a short circuit, or something in-between" you got all 3. well done.

And any dark beer or a nice burbon will do if you want to have one on my behalf, glad i could help out.
 
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