Pair of MEP802a Both Have Voltage/Load Issues

[loca5790]

I have two Mep802a military surplus units I’ve gone through.

The first unit runs great it’s at 35 psi hot under load with 15w40 and is smooth as a top. It has overload tripping issues. I’m running it on Klopps monitoring system and it says the loads at 70% on leg one and 168 on leg 2 and 3. The gauge is at 70. It’s powering a battery charger to charge large battery banks. It will run for about 15 minutes and trip overload. It’s running at 4kw output via the charger. I can’t find anything wrong. I have confirmed leg 2 is dead and it’s single phase

the second unit has 116v out. It’s set 120/240 single phase. The gauge reads 240 but leg 1 is dead. I’ve tried flipping the switch to set output probably 50 times back and forth literally before retesting. It’s got 116 out between L1-L3 and L3 and Neutral. L1 is 0 to anything. I’m leaning towards it being in the selector switch but want to check with you all before I pull it apart.

 

[WWRD99]

I have two Mep802a military surplus units I’ve gone through.

The first unit runs great it’s at 35 psi hot under load with 15w40 and is smooth as a top. It has overload tripping issues. I’m running it on Klopps monitoring system and it says the loads at 70% on leg one and 168 on leg 2 and 3. The gauge is at 70. It’s powering a battery charger to charge large battery banks. It will run for about 15 minutes and trip overload. It’s running at 4kw output via the charger. I can’t find anything wrong. I have confirmed leg 2 is dead and it’s single phase

the second unit has 116v out. It’s set 120/240 single phase. The gauge reads 240 but leg 1 is dead. I’ve tried flipping the switch to set output probably 50 times back and forth literally before retesting. It’s got 116 out between L1-L3 and L3 and Neutral. L1 is 0 to anything. I’m leaning towards it being in the selector switch but want to check with you all before I pull it apart.

There's a guy on here going through some load issues that he found were contact corrosion problems. He used a few cans of Deoxit in the contacts of as many switches he could and it is now working as designed. I am not sure if that is the fix but most say it's the starting point.

 

[Guyfang]

Before you go farther. Lets do one gen set until its fixed or at least we know whats wrong. THEN you start a thread on the second one. Troubleshooting two sets, in one thread will only make people want to shoot themselves. I would suggest set number 2. But that's up to you.

 

[Light in the Dark]

I have encounted phantom overload issues, that have been resolved by thorough deoxidation of the S8 and all other switches and contacts in the machine. Thats where I would personally start on that unit, pull the operator compartment roof, disconnect the batteries, and get to 'cleaning'
(S8 phase switch in particular). If you don't have resolution after doing that, I would glance at the TM related to this machine, and its pertinent testing section.

 

[loca5790]

I read the TM and looked at that section. I can start the procedure. The over load unit had a fire I literally stripped the whole thing down cleaned it and painted it. I had all the wiring and engine apart.

@Guyfang understand your point. I’d like to focus on gen2 as well. Gen 1 I’ll just flip battle switch if needed until I figure it out.

 

[Ray70]

Depending on the severity of the fire damage, I wonder if you have a damaged component or perhaps a misplaced wire?

 

[Light in the Dark]

A more than minute omitted detail about your baseline on this equipment.

 

[loca5790]

It was an alternator fire from the looks of it. The only damage was the alternator wiring and a ton of fire extinguisher media. It may not have even been an actual fire someone just blasted the fire extinguisher. No signs of actual damage.

 

[loca5790]

Here are some pictures of it.

 

[loca5790]

I'm going to take a look at the one with low voltage first. (Only one leg at output despite gauge showing 240v)

Based on the wiring diagram it is most likely at K1. Picture attached for reference. Voltage is measured by S6 selection after S8 so since the gauge is showing voltage it may be a stuck/corroded K1. It's also possible it's a broken wire but I find that less likely.

I'll check voltage at S8, but if I find any issues with S8 Ill probably remove it instead of clean it. Seems like a failure point that is uncessary I will never be switching phases/voltages on these units.

I checked the diagram and traced all the internal connections to verify and both show the same thing:
These tie toegether and land at K1 (AC Circuit Interrupter)
L1 → (T1 + T12)
L3 → (T11 + T3)
L0 → (T7 + T5 + T9 + T6)

These tie together and do not land anywhere
T2 + T8 + T4 + T10

 

[Digger556]

It was an alternator fire from the looks of it. The only damage was the alternator wiring and a ton of fire extinguisher media. It may not have even been an actual fire someone just blasted the fire extinguisher. No signs of actual damage.

To be clear, are you talking about the DC alternator driven by the belt or the AC alternator driven off the flywheel?

 

[WWRD99]

I'm going to take a look at the one with low voltage first. (Only one leg at output despite gauge showing 240v)

Based on the wiring diagram it is most likely at K1. Picture attached for reference. Voltage is measured by S6 selection after S8 so since the gauge is showing voltage it may be a stuck/corroded K1. It's also possible it's a broken wire but I find that less likely.

I'll check voltage at S8, but if I find any issues with S8 Ill probably remove it instead of clean it. Seems like a failure point that is uncessary I will never be switching phases/voltages on these units.

I checked the diagram and traced all the internal connections to verify and both show the same thing:
These tie toegether and land at K1 (AC Circuit Interrupter)
L1 → (T1 + T12)
L3 → (T11 + T3)
L0 → (T7 + T5 + T9 + T6)

These tie together and do not land anywhere
T2 + T8 + T4 + T10

You really have gone all in on getting this one going. That fire extinguisher powder can be very corrosive. I am glad it was the alternator area that got it and not the other side. I wonder if the return hose popped and caught on fire that way. If you can get the K1 switch to work it should make voltage on both legs. That S8 can cause problems too. Hope it cleans up good soon!

 

[loca5790]

Low voltage generator is fixed. Broken connection at ring terminal for L1 lug. Got blessed on this one. Almost shorted on bracket to case.

The fire unit is the one with overload issues. It had brand new break in oil in it and a rebuild tag in paperwork. I took it apart ported cylinder head, decked the head and gasket matched intake and exhaust. It honestly looks like they may have shorted the alternator when hooking up the dc system because the wires are not color coded. The wire ends on the alternator were cut off and the power wire was toasty I replaced it. I was worried it was hooked up backwards and hurt some of the dc was electronics but everything checked out.
I cleaned all the media up and neutralized it the epoxy painted the inside and generator case. I had the generator internals apart and checked for any winding damage. There wasn’t any. I replaced all the fuel lines and rails while I had it apart. All AN lines are now PTFE braided lines.