Question about my 1985 M1008 Gen 2 system

[dsouthwick54]

Hello everyone and thanks for all the great information on this site! I have a 1985 M1008 that as we all know are very tricky to work on when it comes to their electrical system.
I was curious if anyone knew if the Voltage Meter in these trucks has to be working properly in order for the Gen2 light/entire Gen 2 system to work? Mine works.. well it moves when I turn the key on but the gauge get buried all the way to the right. Thank you to anyone who can help

 

[NDT]

All the way to the right in the red field means one of your alternators has a bad regulator and is overcharging. Fix it before driving, you will cook your battery. Verify with a hand held volt meter.

 

[cucvrus]

Quick question. Does Gen 1 and Gen 2 idiot light up when you first activate the key during the wait cycle?

 

[dsouthwick54]

I just had alternators tested and they both passed. Gen 1 light comes on but Gen 2 doesn’t. After I start the truck Gen 1 light goes out. Also I forgot to mention earlier, when I start the truck my Gen 1 Alternator starts heating up quickly, belt starts squeaking. I have enough time to read it’s output before I have to shut it off and it drops to 11.5 volts with truck running.

 

[NDT]

With the truck running put your voltmeter on each battery one at a time and you should read 13.8 volts more or less.

 

[dsouthwick54]

Front battery with truck running was 11.52
Rear battery didn’t change with truck running. Stayed at 12.62

 

[NDT]

If your dash gauge is pegged in the red witb those at battery readings, it’s shot.

 

[dsouthwick54]

Ok thank you! I ordered a new Volt Meter. Will let the thread know if it fixes my Gen 2 problem.
Since my Gen 2 system isn’t working properly would it cause my Gen 1 Alternator to start overheating? (pulley on alternator gets hot but housing doesn’t). Batteries show an under charge issue
Front battery with key off 12.26 volts
Rear battery with key off 12.77
Front battery with key on after glow plugs cycle 12.12
Rear battery with key on after glow plugs cycle 12.77
With truck running front battery is 11.52
With truck running rear battery 12.62

 

[MarcusOReallyus]

You have more than a voltmeter problem. Fix that, since you know it's bad, but you do have other problems.

Do you know if the PO "fixed" any wiring?

EDIT TO ADD: Take a good look at the alternator testing sticky. Might be just what you need. Also, check your fusible links.

(by the way, on a side note, you don't have an 85. You have an 84. The Army didn't want the hassle of dealing with model year changes in their supply chain, so they required them all to be built to 84 specs. When you need parts, you want 1984 parts, no matter if your truck was built in 84, 85, or 86. )

 

[dsouthwick54]

Was worried I had more problems then that.. Not sure if the PO fixed any wiring.
Thanks for all the great info
I will check all the fusible links

 

[nyoffroad]

If the pully is getting hot I'd start with making sure the belts are in good shape and tight. A loose belt will slip causing a squeal and heat, it can also glaze the belt making the condition worse. If in doubt get new belts (good ones).

 

[LT67]

I just had alternators tested and they both passed. Gen 1 light comes on but Gen 2 doesn’t. After I start the truck Gen 1 light goes out. Also I forgot to mention earlier, when I start the truck my Gen 1 Alternator starts heating up quickly, belt starts squeaking. I have enough time to read it’s output before I have to shut it off and it drops to 11.5 volts with truck running.

The Gen 2 light is telling you that an alternator is bad. Trust what the system is telling you.

 

[cucvrus]

The Gen 2 light is telling you that an alternator is bad. Trust what the system is telling you.

This is true. A bad alternator can cause the light to not illuminate. Internal issue. Going forward I am getting self exciting voltage regulators. The idiot light still works but it will eliminate the need to excite the charge circuit. On my M1028 I just floor it and it moves the needle to the tick mark in the green.

 

[MarcusOReallyus]

On my M1028 I just floor it and it moves the needle to the tick mark in the green.

You're just always looking for an excuse to floor it, Rick.

 

[cucvrus]

I have never explained it before, and I will not now, here. I always floor it when I pull out and am met with the same resistance and ignorance from the same select few passengers. I simply dont care to debate it anymore. The CUCV charging system can be complicated. I just make it simple. Floor it and watch the needle just POP into place at the tick mark. It's a simple task. Beats changing the alternator at the moment. It still works every time. Good Luck, Have Fun and Be Safe. Life is a Highway. Drive it.

 

[MarcusOReallyus]

 

[cucvrus]

 

[dsouthwick54]

The Gen 2 light is telling you that an alternator is bad. Trust what the system is telling you.

Both alternators are fine. It was an in line fuse.