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Discussion Starter · #1 ·
I just bought my 94 Sidekick a few days ago and have begun the debugging process. I can fix most things but wiring probs wear me out and I've got one.
The issue: Low beams work & appear equally bright, but driver side high beam is out. Passenger side high beam works. Both bulbs are new and I've checked connections for corrosion. I've opened the combo switch and, as best I can tell, is ok. Both fuses (L/R HL) look ok. I have a so-so wiring diagram and think I follow it: white/blue & white/red always hot; red/white low beam lead; red high beam lead. (Someone correct me if any of this is wrong.) Now this is where I get lost. From what I've learned the HL's are switched to ground at the combo. But I have yet to get my test light to come on at either side's solid Red wire. Even worse with the HL switch off the red/white is hot. Switch on and red/white is cold but both lows work. The white/blue-red is always hot no matter what. Switch on high and red/white is hot again. If I take both bulbs out the red/white goes dead switch on/off. Put either bulb in and red/white is hot switch off. I suppose the whole switch to ground is part of my confusion but something else is wrong. Please help! This is my 1st Suzuki so I'm just starting to learn and want to fix it right. Mine is non-DRL if that even applies here.
 

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I added my comments in Bold

I just bought my 94 Sidekick a few days ago and have begun the debugging process. I can fix most things but wiring probs wear me out and I've got one.

Low beams work & appear equally bright, driver side high beam is out. Passenger side high beam works.
Both bulbs are new and I've checked connections for corrosion.
I've opened the combo switch and, as best I can tell, is ok. // hope you haven't damaged anything. :eek:

Both fuses (L/R HL) look ok.
white/blue & white/red always hot; // Power to each headlight. means fuses are OK
red/white low beam lead; red high beam lead. // yes. Grounding either should light the corresponding high/low bulb.

(Someone correct me if any of this is wrong.) // you have it correct.
Now this is where I get lost.

From what I've learned the HL's are switched to ground at the combo. // yes.
But I have yet to get my test light to come on at either side's solid Red wire. // you should have power when the high beams are OFF. When they are ON you should see ground. <-- This is where your problem is.
Even worse with the HL switch off the red/white is hot. // Normal. Should be hot any-time the light is off. (power is "seen" through the bulb.)

Switch on and red/white is cold but both lows work. // Normal, you are seeing the ground applied to make the lights work,

The white/blue-red is always hot no matter what. // normal. as long as fuses are good.
Switch on high and red/white is hot again. // Normal, the low beams are off. The ground has been removed.
If I take both bulbs out the red/white goes dead switch on/off. // Normal. bulbs removed = no power through them.
Put either bulb in and red/white is hot switch off. // Normal. good bulb installed = power seen through it.

I suppose the whole switch to ground is part of my confusion //Yup... confuses many.
but something else is wrong. // as one high beam doesn't work... yes.

Please help! This is my 1st Suzuki so I'm just starting to learn and want to fix it right.
Mine is non-DRL if that even applies here. // DRL uses low beams... It shouldn't cause issues with high beams.
If you have a problem with a single filament of a single headlight, there are not very many places for it to be bad. Basicly, from the bulb to the splice that connects to the same filament (high/low) for the other side.

-- When troubleshooting a ground switched circuit, remember that power is always applied to the load. (The bulb in this case.) So it will have power at all points on the switched side of the load when the switch is OFF. But when the switch is ON, the load drops "all" the voltage, so you should see ground at all points on the switched side of the load.
-- In a ground switched system the power seems to run "backwards." So your test lights and voltage readings will seems "backwards" to someone used to power switched systems.
-- In a ground switched system, you can troubleshoot by GROUNDING places along the switched side of the load. (The load will drop the voltage, so you are not actually shorting it out.) Just be VERY SURE you know what you are doing... grounding power without a load can burn things up! :eek:
-- Are you positive the bulbs are good? (Swapped them with the same result?)
-- Remove the "good" bulb from the circuit (disconnect it) when troubleshooting one "bad" side. Then power only gets through "good" connections on the side you are working on and not "back fed" from the other (good) side.

If I was going to guess... I bet the connector right at the driver side bulb is bad.
 

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The red wire that goes from the combination switch splices behind the dash, just left of the steering column. One splice goes to the right headlamp, one to the left lamp and one to the hi beam indicator on the dash. If you are advising that, of this circuit, only one lamp does not work, either the hi beam filament in your headlamp is bad (connect it to the other headlamp connector to confirm if it works), and if it does the red wire from the splice to the specific non working bulb is problematic. So check that wire. Basically, as Mike says, if you think of a circuit as circular, the circuit goes from power to load (like your bulb) to switch to ground. When the switch is off, you will have voltage on both sides of the load or bulb, all the way up to the open (off) switch. When the switch turns on, it is allowing the ground to pass through it, and provides ground to the to the bulb, so, once the switch is on, you have, for example, 12v on one side of the bulb, and 0v (ground) on the other.
 

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White/blue, white/red (lamp feeds) are always hot.

Red/white is the low beam and should be hot when low beams are NOT on, it should go cold when they have been selected.

Red is high beam and should be hot when high beams are NOT on, it should go cold when they have been selected.

Working with a test light can be misleading - it lets you know there is voltage but not what the voltage is, and because this is a negative switched circuit it can trick you - if a test light is all you have to work with, remove both bulbs and probe the white/blue & white/red wires - both should be hot, if not, there's a blown fuse or broken wire.

If both are hot, probe the red wire with the switch off - it should also be hot at this time because of the high beam dash indicator, the red/white wire should be cold.

Install the driver's side lamp ONLY and probe red & red/white, both should be hot, switch on and select low beam, red should be hot, red/white should be cold, low beam should be lit - select hi beam, red should be cold, red/white should be hot - hi beam should be lit - if you're not getting these, there's a switch or wiring problem.
 

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Discussion Starter · #5 ·
Thanks for the replies. It makes me feel better to know I had at least some of it figured out and rest is helping me learn. Luckily I found the prob while chasing another one down. The driver side red wire (high beam) had a break in it. I just happened to be moving the harness out of the way and noticed corrosion. There was a 2" section that had been damaged in what may have been a little fender bender. Thanks again ya'll.
 

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... I found the prob ...The driver side red wire (high beam) had a break in it. I just happened to be moving the harness out of the way and noticed corrosion. There was a 2" section that had been damaged in what may have been a little fender bender. ....
Pretty much what i said in my first post on this subject.

If you have a problem with a single filament of a single headlight, there are not very many places for it to be bad. Basicly, from the bulb to the splice that connects to the same filament (high/low) for the other side.
Good to hear it was solved.
 

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Discussion Starter · #7 ·
I felt kinda stupid when I found the prob. I was convinced it would be something really obscure especially since wiring drives me bonkers. I had looked everywhere but the most obvious spot. I'm super impressed with the good responses I got. You guys are on it. Plus it makes me feel good to learn from those in the know.
 

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Be prepared for getting 'bonkers' more often. Wiring is becoming an issue on these old cars. Glad it's sorted.
 
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