Mep 803a No/Low Low Power Output

[Iron.Horse]

Good Evening Guys,

First post/new member here, but long time lurker. I really want to thank you all for your imense knowledge on everything military, I have owned a couple military trucks, but this is my first military generator I am messing with. Please forgive me for my electrical ignorance, I do have the TM printed and have been trying to follow it, as well as researching these amazing forums for more hours than I care to admit, but I am definitely far from an electrical engineer.

I am working on a 2006 MEP 803a that I bought non-running but private party and was told "it ran and produced power 9 months ago", but I am starting to doubt that statement. I have spent the last few weeks working on the mechanical side - new water pump (old one was leaking from weep hole), misc fuel lines, return lines, filters, fluids, belt, fuse mod, stuck injection pump or two, etc. Finally got it running, and it's purring like a kitten. Starts easy, minimal smoke, doesn't seem to be wet stacked, throttles up and holds RPM's well, coolant temps seem good, batteries seem to be charging. My issue is on the electrical side, the unit produces little to no power. No discernable readings on the V or HZ gauges, but the circuit interupter switch seems to work, green light comes on and seems to stays on until I disengage it. I am getting 7 VAC at the convenience plug, and the same tracing the wires back beyond the GFI breaker. I believe my main lugs are similar voltage. Checked the fuse continuity on the recently installed fuse mod which I made sure to put in place before running the unit (thanks kurtklopp), and it appears to still be good. S1 switch is getting around 21.3v at pin 7 when holding at start position, which seems a bit low for the exciter? A1 pins 5 snd 6 are about the same 21vdc with the switch held, and drops to 1.8-2 vdc in run position. CB1 was pulled out/tripped when I was first attempting to start the unit, but has since not been an issue. I took the top pannel off, got rid of a massive mouse nest, sprayed some electronic cleaner in all of the switches and ran them back and forth to try and clean up the contacts a bit. Kind of stuck at this point scratching my head. Any advice is greatly appreciated!

 

[Iron.Horse]

Hopefully these work, I know pictures are appreciated...

 

[2Pbfeet]

Welcome!
Congrats on getting it purring like a kitten.
Which TMs do you have and have you read?
The fourth photo has what looks the remains of rodent nest. If it were me, I would start by cleaning out the debris (fire and short risk), examine that area for wire damage, and clean off the mouse urine as it is pretty conductive. Don't over look the current sensor pass through that seem full of debris. Are the red flakes in the debris pieces of terminal insulators? After cleaning the general area and the switch in particular, and making sure that the generators is OFF, I would check that the switch there (S8 ) is clean by using some DeOxIt in it and cycling the switch until you are tired, and then a bunch more.

There is a really nice troubleshooting flow chart in the TM.

All the best,

2Pbfeet

 

[Light in the Dark]

Start with the batteries, if you are only measuring 21V, I am surprised its even starting up. From the -24

22. GENERATOR SET FAILS TO GENERATE POWER.
Step 1. Test for defective ac circuit interrupter relay (K1), paragraph 2-61.3.
a. If AC circuit interrupter is not defective, do Step 2.
b. If defective, replace AC circuit interrupter, paragraph 2-61.
Step 2. Test for defective Field Flash relay (K15), paragraph 2-33.2.
a. If defective, replace Field Flash relay.
b. If Field flash relay is not defective and trouble persists, notify next higher level of maintenance,

This info is found in TM-9-6115-642-24.

 

[Iron.Horse]

Welcome!
Congrats on getting it purring like a kitten.
Which TMs do you have and have you read?
The fourth photo has what looks the remains of rodent nest. If it were me, I would start by cleaning out the debris (fire and short risk), examine that area for wire damage, and clean off the mouse urine as it is pretty conductive. Don't over look the current sensor pass through that seem full of debris. Are the red flakes in the debris pieces of terminal insulators? After cleaning the general area and the switch in particular, and making sure that the generators is OFF, I would check that the switch there (S8 ) is clean by using some DeOxIt in it and cycling the switch until you are tired, and then a bunch more.

There is a really nice troubleshooting flow chart in the TM.

All the best,

2Pbfeet

I believe I have the Marine Corps TM, it's quite long, several hundred pages I would say. The guy at the UPS store had fun spiralizing it. I like the paper becuase I can reference it while working on the unit. I am not super comfortable/knowledgable in the electrical world and putting power/jumper cables places they don't belong doesn't usually work out well for me...

I did remove the mouse nest, and your right, the urine is quite corrosive. the screws in the bar below the nest were a bit challenging to remove because they were so rusted. Got that cleaned up and replaced most of the screws with 8-32 grounding screws that have the hexagonal top. I have been looking for chewed, rubbed, or messed up wires, but nothing bad in that area yet. Thanks for your advice on the S8, I will will try to keep working that switch.

 

[Iron.Horse]

Light in the Dark, thanks for your wisdom, the S1 is where the lower voltage is, I have just over 25v at the starter with brand new batteries, and the alternator seems to be maintaining them. Unit fires right up no problem.

I know I have read through most of what you quoted from the manual, I just don't have a ton of confidence in my abilities with a volt meter or keeping up with the manual. Definitely trying to learn though. I reached out to a few local people that have some level of experience with military hardware, hoping that I could get knowlege and/or pay someone to trouble shoot it. Unfortunately everyone I talked to has said that the generators are complicated and confusing, and they basically swap parts until something works. Even if that means cobbling together multiple machines to make one working unit.

 

[Light in the Dark]

If you can figure out what you wife wants for dinner at least once a week, you can work on an MEP.

The DC voltage should be the same across the system, so you have already started to diagnose the issue!

Study the wiring diagram (both on the door, and in the TM if need be, as it has info about which contacts on S1 are discrete, and which are bonded to others).

Corrosion is a known issue on these sets, in contacts. Refer back to what 2pb wrote, good info). Deoxit is magic in a bottle. Buy 3-4 cans, use liberally.

Understanding the directional flow of the DC system will help you determine where (and hopefully why) voltage is dropping out.

 

[Toolslinger]

And... When you need a break from your brain melting down from trying to understand it all, take some time and put some 1/4" mesh screens over the various openings. (Side, Top, and 3 on the Bottom)

You for sure do not want to go through the trouble to clean up the current mess, and get running again, only to let a rodent move back in and ruin all your work.

 

[Toolslinger]

Taking another look at pic 4... If you don't have a single chewed wire with that much mouse detritus, you should be buying a lottery ticket.

As mentioned above, that 21v is an issue. If you're batteries are good, and putting out 24 together, and you've got 21 down the line, there's resistance someplace chewing up voltage. Resistance means heat, and heat leads to fire, and or melted wireing. It is much easier to find the source of the issue if you let it burn, but it will be a whole lot more work and money to put it right... Don't ask me how I know that...

 

[Iron.Horse]

Ok, so did the 2-61.3 testing procedure, A1 and A2 are 3.0, B1 and B2 are 3.0, C1 and C2 are 457? Weird. Not entirely sure what we are testing "12" against. Connected jumper wire and there doesn't seem to be any continuity between any of the terminals. Pulled k15 as outlined in 2-33.2, none of the terminals had any reaction on the meter except for 7 and 4 which reads 42.6. Is this indicating a bad K15?