On going battery discharge problem M1009 CUCV

[bcr226]

Need a bit of technical advice guys... my M1009 has been having a battery discharge problem and I can't find out where the problem lies. Every 60 days, I have to switch the front and rear battery on the truck otherwise, the rear battery looses the charge and won't start the truck.

I replaced the alternator on the right side of the engine. After I did this, I began getting the glow plug fuze blowing out. Then two wires burned out. I replaced the wires and all seemed okay until this morning. I started the truck today and the engine turned over very slowly but it did start.

I'm at the end of my knowledge on this issue. I know guns not electronics. Can anyone give me any advice on what I need to do?

Thanks,

Mike

[kruser79]

The CUCV charging and starting systems are some of the most poorly designed systems on military vehicles that I've seen yet. I hate to tell you this Mike, but our troubleshooting would often yield a faulty part. We'd replace this part only to have one of two things happen. Either it required something else (that didn't show up during the troubleshooting) to get the vehicle up, or it would be FMC (Fully Mission Capable) for a little bit, only to go down again.
It got to the point where (and this goes against every maintenance-minded bone in my body) if we got one with a charging problem, even something as simple as low charging voltage, we'd replace both alternators and both batteries. This was an act of desperation after constantly having our four CUCV's brought back right after we had fixed the problem they originally came in for. Something about the way they designed these two systems caused them to have a "trickle effect" failure path. We found this out by watching ours after having them come in time and time again. One would come in with charging problems, we'd find one bad alternator and change it. It'd come back after a week or so with charging problems again. Might be the same symptoms, might not. But some other component would be found faulty, and we'd change THAT. Another week or three, it'd be rrrrrright back in my shop! Another round of troubleshooting, another bad part, another new one went on. I've been at this for a long time, and my boys at that time were very good, so it wasn't a case of, "You guys just didn't know what you were doing, and arbitrarily changed parts." Every single time these vehicles were broke, we troubleshot, found something bad and changed it. When the truck left, it was up, charging away, or warming away (if it was the glow plug system-we had problems like this with both of those systems).
But it led me to think that these components relied on each other so heavily that when one failed and was replaced, the others just couldn't "mesh," and failed, one by one. When we started looking at it this way, we came up with the idea of changing out these components:
Charging system-both alternators, both batteries, the resistor coil, and the junction block.
Glow plug system-ALL the glow plugs (never change some of them, always change them all), the glow plug controller, and the temp sensor.
I know this doesn't help with your specific problem, but it sounds like you have either a problem with the charging voltage coming from one alternator, or with the cables that run to that one battery. It's just that even using the troubleshooting procedures in the manuals, it's not always a simple matter of "that piece is bad, replace it."
But I'd start with looking at the voltage being put out by both alternators, and following it all the way to each battery. It's a start anyway.

[bcr226]

Thanks bro,

that gives me a good place to start. For now, I put a portable charger/battery booster in the truck so I don't get stuck.

Mike

[kruser79]

You also might want these?

[kruser79]

Hey Mike, I'll leave the schematics here for awhile. Then I'm going to take it back, but I'll upload it to TP for safe keeping somewhere (but them tankers like to keep us mechs in the closet, lol).

[BTDT]

I have a 1009 and 1010. The 1010 is currently down due to a failed battery. Thanks for posting that info regarding "meshing" and total failure. My 1010 has gone through 3 batteries so far in the last 4 years. My local shop, which loves to work on my trucks "'cause they're cool" checked the electrical system and found the #1 batt had failed.


Q: should I replace #1 only or both?

Thanks,

[kruser79]

Originally Posted by BTDT

I have a 1009 and 1010. The 1010 is currently down due to a failed battery. Thanks for posting that info regarding "meshing" and total failure. My 1010 has gone through 3 batteries so far in the last 4 years. My local shop, which loves to work on my trucks "'cause they're cool" checked the electrical system and found the #1 batt had failed.


Q: should I replace #1 only or both?

Thanks,

The problem isn't so much that the battery failed. I can almost guarantee that something caused it to fail. That's what is going to give your shop fits, "What is causing it to fail?" Modern batteries can be left in place for as long as 10 years (No guarantee as to how studly it'll be, but I've seen 'em). So to have it go out so often, tells me that you have a weaker link somewhere. Some of the things to look at would be output of both alternators, the Engine Wiring Harness Block, and even the Suppressor (between the two terminal boards). Here, I'll leave this up for a bit. Then I'll send it to Jason to post in the Vehicle Specific forum down in Downloads.