M929a2 battery drain

[Neeko21]

Hello everyone,
I think I’m having problems with my PCB. I have a 2.5 amp draw when truck is off. I have also noticed that my truck will start with battery switch in off position. I did a little checking with power probe and noticed I have voltage on both terminals C&D of PCB harness. From what I am reading on schematic only one should have voltage until battery switch is turned on. Hopefully u experts can help. Thanks

 

[simp5782]

Pop the cover on the pcb. It just snaps on. See if you have power on the bottom solenoid on the small posts. This turns the solenoid on. Just to check if you have or Don't have a bad battery switch that is allowing that solenoid to stay on

 

[Neeko21]

Checked bottom solenoid, and it closes when I flip switch. The problem I am having is that terminal D on PCB harness with it disconnected from PCB box. So when harness is hooked up to PCB and cover is off I have 24 volts on both sides of solenoid with switch off, kinda like a stuck solenoid, but that’s not it. Terminal D of PCB harness has 24 volts when it unhooked from PCB. Thanks

 

[simp5782]

Pull the starter switch out and see if wire 5 at the pcb drops the power. If no we will chase the voltage at the circuit breakers.

Diagrams below

 

[Neeko21]

Pull the starter switch out and see if wire 5 at the pcb drops the power. If no we will chase the voltage at the circuit breakers.

Diagrams below

I pulled wire 5b off my ignition switch and it did not drop the power. Is that the wire you are referring to? Thanks.

 

[simp5782]

I pulled wire 5b off my ignition switch and it did not drop the power. Is that the wire you are referring to? Thanks.

Yes.

At the alternator. Remove wire 568 and check your voltage at D.

Assuming you have the stock alternator. If you don't this wire should be taped up. This is an exciter wire that has a diode in it.

 

[Neeko21]

Yes.

At the alternator. Remove wire 568 and check your voltage at D.

Assuming you have the stock alternator. If you don't this wire should be taped up. This is an exciter wire that has a diode in it.

Yes I do have a stock 60 amp alternator. It does charge when truck is running. I will check that wire hopefully tommorow and get back to you. Thanks for your help

 

[simp5782]

Yes I do have a stock 60 amp alternator. It does charge when truck is running. I will check that wire hopefully tommorow and get back to you. Thanks for your help

That wire 568 let's power go from where 15,5,568,5b all meet to the alternator telling it to charge. However it has a diode to only let power go to the alternator. If it's bad it is letting power from from the alternator to bleed across

 

[Neeko21]

Thanks again and I will try to make it out to truck to test. Did u want me to test with PCB harness disconnected? Thanks

 

[simp5782]

Yes. Any testing should be done with it disconnected

 

[Neeko21]

Yes. Any testing should be done with it disconnected

Thanks again for all your help. I will post as soon as I can get out to truck. Have a good weekend

 

[Bill Nutting]

Hey Neeko21. Welcome to the site. You’re getting help from one of the best here.
Are you in Clinton Township, Michigan?

 

[Neeko21]

Hey Neeko21. Welcome to the site. You’re getting help from one of the best here.
Are you in Clinton Township, Michigan?

Yes

 

[Bill Nutting]

I’ll PM you...

 

[Neeko21]

Yes. Any testing should be done with it disconnected

Tested today and it does have power. Disconnected alternator and I still have power. Started following diagram and I ended up at diagnostic port. Looks like water has been dripping on it. I removed port from hanger and my ohm meter goes nuts when I hold wires and twist port. Do I need the diagnostic port? Thanks

 

[simp5782]

Tested today and it does have power. Disconnected alternator and I still have power. Started following diagram and I ended up at diagnostic port. Looks like water has been dripping on it. I removed port from hanger and my ohm meter goes nuts when I hold wires and twist port. Do I need the diagnostic port? Thanks

No you don't

 

[Neeko21]

No you don't

Thanks for getting back to me. Just cut all wires out and cap them?

 

[simp5782]

Or cut the one 5 wire and cap it. Since it's your draw.

 

[Neeko21]

Thanks again for all your help

 

[Neeko21]

Thanks again for all your help

Or cut the one 5 wire and cap it. Since it's your draw.

Did some more work with ohm meter and I think the diagnostic port is all corroded inside. Think I’m going to cut off and cap wires. Thanks