[L84sky]

I have no idea where to go from here!

Are you saying the high-current devices (headlights, blower fan, electric windows) are pulling down the battery voltage to the point where the 4WD pump no longer runs?

That could happen if you had unwanted resistance somewhere between the battery's positive anode and the far side of the 80-amp BATT fuse.

Try running your headlight test while monitoring the battery voltage on pin 16 of the DLC. A noticeable drop in voltage on pin 16 could indicate a resistance in the supply line. On my car pin 16 supply's voltage to the PCM and the PCM supply's voltage to my 4WD actuator pump. Technically the DOME fuse supply's the voltage to the PCM but you can monitor it at pin 16 of the DLC.

 

[Marc postle]

If you are saying the high-current devices (headlights, blower fan, electric windows) are pulling down the battery voltage to the point where the 4WD pump no longer runs?

That's what i thought when i was testing without the engine running because the battery voltage was going below 12v but running i have over 14v and it was still doing the same thing.

I did the test you said and these are the results
Pin 16
Engine off
Heat lights off 11.7v
Heat lights on 10.4v

Engine running
Head lights off 13.9v
Head lights on 12.8v

 

[L84sky]

I just ran the pin-16 "engine off" test on my car:
Head lights off 12.28v
Head lights on 11.62v
I'm losing 0.66v. You are losing 1.3 volts. That's a lot. I'm not sure the PCM can operate on 10.4 volts.

The smaller battery cable goes to the 80-amp BATT fuse. With the headlights ON, look for a 1 volt drop between the copper wire and the center of the battery anode. On my car that drop is only 55 mV.

 

[aquanaut20]

Rather than follow voltage, have you considered using an amp clamp on the feed to the pump to ascertain what it is using.(amperage..).

It is a fact, you can have voltage but little to no amperage.. Also if you are testing with voltage you MUST load the circuit.. open voltage is useless..

 

[Marc postle]

First thing I'm going to do is chuck a new battery on as mine seems to be on the way out, i can't see it being the cause because i still have the problem with the engine running but it sits at 12.4.v even after I've been driving it all day.

Then i will check the battery cables like you say and see what happens.

I haven't got a clamp meter but i will see if someone at work has one next week and use that to help

 

[aquanaut20]

Changing parts without proper testing is my main beef,, LOAD test the battery, chuck a new one in if it fails..

 

[Marc postle]

Changing parts without proper testing is my main beef,, LOAD test the battery, chuck a new one in if it fails..

the battery with headlights on is reading 11.6v that's had it hasn't it?

On another note, I've been out this afternoon filling up feeders in the fields and woods, everything switched off and its stayed on and worked the whole time

 

[aquanaut20]

The key would be what is the recovery voltage and time for recovery once HL are shut off..

 

[2013GV]

the battery with headlights on is reading 11.6v that's had it hasn't it?

On another note, I've been out this afternoon filling up feeders in the fields and woods, everything switched off and its stayed on and worked the whole time

Nope, thats a common sort of drop if engine isn't running.

 

[Marc postle]

The key would be what is the recovery voltage and time for recovery once HL are shut off..

ok, i'm not great with electrics as you probably guessed. Can you give me an example of a test to perform and i will put the results up

 

[2013GV]

Test what.? Battery load test is not easy to do with basic tools, but if it cranks and starts ok after the headlights have been on for 5 minutes thats a good indicator its ok.

 

[L84sky]

the battery with headlights on is reading 11.6v that's had it hasn't it?

11.6 is not the problem. It's the drop to 10.4 that's the issue. Here's why.

In a good circuit (top) the voltage at pin 16 is the same as the battery voltage.
In a circuit with some unwanted resistance at the battery connector (bottom) the voltage at pin 16 is noticeably lower.
This example assumes each headlight draws four amps. If the current is higher the voltage drop will be greater.
The point is the battery voltage didn't change, you just lost 1.1 volts across the 0.15Ω resistance.
You can measure the voltage drop across the 0.15Ω resistance with your voltmeter.

 

[Marc postle]

11.6 is not the problem. It's the drop to 10.4 that's the issue. Here's why.
View attachment 105272
In a good circuit (top) the voltage at pin 16 is the same as the battery voltage.
In a circuit with some unwanted resistance at the battery connector (bottom) the voltage at pin 16 is noticeably lower.
This example assumes each headlight draws four amps. If the current is higher the voltage drop will be greater.
The point is the battery voltage didn't change, you just lost 1.1 volts across the 0.15Ω resistance.
You can measure the voltage drop across the 0.15Ω resistance with your voltmeter.

Thank you, I think I actually understand your explanation.
So I need to look for voltage drop which is caused by resistance and resistance would be caused by what? Damaged wires, bad connections, bad earths???
And I need to look between the battery and battery fuse? Or everywhere?

 

[2013GV]

Bad connections are probablythe issue, just because they are tight does not mean they are good. Check all connections especially the grounds to the body from the battery. Remove, sand or clean both surfaces so they are bright and shiny, bolt back up. Many small corrosion points add to a big issue, a small resistance across several connections adds up

Even the main fuses get corrosion on the terminals

 

[Marc postle]

Bad connections are probablythe issue, just because they are tight does not mean they are good. Check all connections especially the grounds to the body from the battery. Remove, sand or clean both surfaces so they are bright and shiny, bolt back up. Many small corrosion points add to a big issue, a small resistance across several connections adds up

Even the main fuses get corrosion on the terminals

Great thanks, I will do as much as I can tomorrow,
I’ve got some dielectric grease so I will put that on the connections once cleaned.
I will report back tomorrow 👍

 

[L84sky]

And I need to look between the battery and battery fuse? Or everywhere?

Set your voltmeter to the 2-volt range. With the headlights ON measure from the battery post to ATC fuses.

The ATC fuses are the blue ones under the hood.

Put your black lead on the metal tabs (either one). If there is no unwanted resistance the meter reading will zero. If you have a volt or more you could have corrosion.

 

[Marc postle]

i've just been out to make a start and i've noticed i have 2v between the negative terminal and any body earth, is this normal before i carry on?

That was ignition on and head lights on

 

[2013GV]

Nope, thats an issue, should be under 0.1V battery negative terminal to body, and same to engine block.

If you're measuring from battery terminal post to ground lug on body, you have a bad connection at battery post, or a bad ground lead, as in the crimps are corroded internally, got a jump start cable? Go battery negative to a nice clean body point remote to the point the existing lead is connected then measure again, if voltage goes way down, that is proof its in the ground lead,

 

[aquanaut20]

That means you have a serious issue with the ground..

 

[L84sky]

is this normal

You have unwanted resistance somewhere in the ground circuitry. Use 2013CV's technique to jumper around the ground connections until the 2-volt drop goes away. You can use a meter lead for this because you are only dealing with headlight current. Jumper cables would only be needed if you were trying to draw 500 amps.

The jumper will provide a path around the unwanted resistance. When you jumper the bad connection the voltmeter reading will head towards zero.