Electrical Dip

[MarkM]

Quick question are these batteries the same model and also do the share the same lot number.

 

[Mogman]

looking at the metal tags between 2a and 568 is where I get 17.7v and between 568 and 68a is where a get 13.1 all on the regulator.

I cleaned most of the vehicle grounds when I got it including the one on the alt and starter but I'll look over all the connections a little more.

You should be looking from the terminals to ground, not to each other. completely ignore 2A for now, it is an ac signal that tells the PCB the engine is running.
568 is the alt exciter (IGN) terminal, it should be 27-28V or so to ground when running.
If you are getting 28.8V at the alt and 26.7V at the batteries you have a wire issue, there should not be that much drop, those are enormous cables and with fresh hot batteries there should be very little drop...

 

[Mogman]

The 14V post on the reg should be around 14.4 to ground, again not measured to any other post.

 

[Mogman]

Another thing you can look at is the voltage from the 14V tap on the reg to ground and the rear battery when not running, they should be exactly the same..

 

[thompsoncustom]

I think I found the problem



I have 28.8v at the bolt with the arc marks behind it but only 26.7v at the block behind it.

bolt was to loose which is why it was arcing at some point im sure. Pulled the bolt and cleaned up the cable, bolt, and block.

now I got 28.8v at the batteries will have to get some time on them to see if there both charging evenly but hopefully that does it, thanks to everyone for all the help.

 

[Mogman]

Glad it looks like an easy fix, that was one of the connections I was talking about.
The cable on the other side is the main ground, it goes to the starter, should even start better!!!

 

[Milcommoguy]

That shunt bolt (being loose) is a common problem. On the back side of battery box, tunnel and frame... that during some demils GI Joe's remove the radio power feeds and in a hurry don't get to tighten them back up as in can you say finger tight. Same for the positive lead.

Battery feed circuits are simple in concept need PMCS. Battery box to starter to harness and if a 4 speed 14 volt half tap follow those thru to TCM power panel / breaker. There is a chance that start boxes and regulators could fail due to a loose nut... Ahh, bolt.

Smart to disconnect all of those circuits / wires and tag for location, pull the batteries, again... wire brush all terminals, lugs clean, replace, check and tighten. Good for another 30 years. IMO Same as the fuel system headaches.

Sparks could fly or more, CAMO

 

[thompsoncustom]

Glad it looks like an easy fix, that was one of the connections I was talking about.
The cable on the other side is the main ground, it goes to the starter, should even start better!!!

ya you got me thinking I cleaned the ground on the starter and on the alternator but not what feeds the battery box area and I was able to track it down with the multimeter.

 

[thompsoncustom]

well not out of the woods yet.

so started the humvee and let her warm up and then picked up some stuff around town, I noticed that the voltage gauge no longer flutters its rock solid like all the other gauges. when I got home I checked the voltage at the batteries and got 25.1v

I shut it off and went inside but decided to come back out and check it at the alternator. started it up and got 28.8v so I pulled the seat again and checked the batteries and got 28.8v at the batteries.

so I'm not sure what's up with the random voltage? Bad voltage regulator?

 

[Mogman]

well not out of the woods yet.

so started the humvee and let her warm up and then picked up some stuff around town, I noticed that the voltage gauge no longer flutters its rock solid like all the other gauges. when I got home I checked the voltage at the batteries and got 25.1v

I shut it off and went inside but decided to come back out and check it at the alternator. started it up and got 28.8v so I pulled the seat again and checked the batteries and got 28.8v at the batteries.

so I'm not sure what's up with the random voltage?

You should have seen the difference in the volt meter.
If it charges when cold then drops off as it gets fully warmed up that could be a bad regulator.
You may still have poor connections, have you checked the positive connections where it goes through the battery box bulkhead on both sides?
The positive bulkhead connector outside of the battery is box PITA to get to and is normally where the 200A alt connects.

 

[thompsoncustom]

You should have seen the difference in the volt meter.
If it charges when cold then drops off as it gets fully warmed up that could be a bad regulator.
You may still have poor connections, have you checked the positive connections where it goes through the battery box bulkhead on both sides?
The positive bulkhead connector outside of the battery is box PITA to get to and is normally where the 200A alt connects.

I haven't pulled the positive on the back side of the battery box yet raining outside today but I'll make sure I do and clean it up.

drove around some more and let it get good and warm then checked voltage at alt and battery and had 28.8v so just kind of random at this point.