Mep831a no output voltage.

[DD58]

Hello to everyone. I just got my self into a mep831a. It’s wasn’t a new idea to me to get a military gen set. I’ve always wanted a mep805 30kw. Any ways the engine run good doesn’t smoke very much little in the beginning then nice and clean. There’s no voltage output to the 3 pins or the courtesy outlets. K12 relay has a green light on it. The electric start works most of the times. Yesterday I unplugged the 2 9 pin connectors off the inverter check the ohms nothing was showing up. Ran the gen set was getting 135vac on 3 different legs. Now I’m not the greatest with an electrical diagram nor a multimeter. But everything else seems to work just right. The preheater secondary fuel pump. There is no fault light on. Other than the low oil pressure light when first starting. I ran it for about an hr yesterday while I was testing voltages so I’m assuming if there was moisture egress into the inverter it should have been gone by then. The only thing that bothered me is the gen set is from 2002 and the inverter is from 2007. So to me that means it was changed. Not sure if there’s something underlying causing it to go bad. I look forward to learning a lot on here and I’m sure this won’t be the only piece of military hardware I have to explain to the wife. I’m the near future.

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[DieselAddict]

Have you verified everytihing is plugged in correctly? I see a MOLEX connector floating in one of the images.

There is a row of input connectors down the side of the inverter that should be plugged in to the harness that leads from the PMA.

 

[kloppk]

The LED inside K12 indicates the set detected a fault and has cut power to the governor controller in an attempt to shut the engine down.

The battery charger is missing from your 831.

The factory fuel filter has been replaced with some other type of fuel filter.

When pull starting the Low Oil Pressure light will come on. Need to clear it using the directions on the Pull Start Data plate.

 

[DD58]

Have you verified everytihing is plugged in correctly? I see a MOLEX connector floating in one of the images.

There is a row of input connectors down the side of the inverter that should be plugged in to the harness that leads from the PMA.

I was checking voltage on the incoming wires to the inverter. I just took the photo before I plugged it back in. All 3 connectors are currently plugged in. Good eye tho.


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[DD58]

The LED inside K12 indicates the set detected a fault and has cut power to the governor controller in an attempt to shut the engine down.

The battery charger is missing from your 831.

The factory fuel filter has been replaced with some other type of fuel filter.

When pull starting the Low Oil Pressure light will come on. Need to clear it using the directions on the Pull Start Data plate.

Oh so the green light on k12 is a fault light. I thought there would be a little red led in it. Ok that makes more sense.
The guy I got it from changed all the fuel lines and filter he said the bowl on the original filter was cracked and leaking.
The low oil pressure light I can get to clear but now that I know k12 is detecting a fault I’m going to have to dig deeper into it. Does k12 run the fault led panel?


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[kloppk]

Relay K12 (the leftmost one) is controlled by the Fault Panel and the Short Circuit relay inside of the inverter.
If the Fault Panel detects a fault or if the inverter detects a Short Circuit it sends power to the coil of K12 causing it's contacts to open/close and cause the LED inside of K12 to go ON.
Once a fault is detected the K12 relay latch's in the Fault position and stays latched until S1 is moved to the STOP position.

 

[DD58]

Relay K12 (the leftmost one) is controlled by the Fault Panel and the Short Circuit relay inside of the inverter.
If the Fault Panel detects a fault or if the inverter detects a Short Circuit it sends power to the coil of K12 causing it's contacts to open/close and cause the LED inside of K12 to go ON.
Once a fault is detected the K12 relay latch's in the Fault position and stays latched until S1 is moved to the STOP position.

Ok. So if I unplug the connectors to the inverter will it give a fault? Because of them not being plugged in. Kinda a Rudimentary test for an inverter fault. Also will not having a 24v battery charger cause a fault.


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[kloppk]

If you unplug all 3 white connectors from the inverter the inverter will be disconnected except for it's 3 output terminals.
At that point the inverter will not be receiving any power from the PMA and all the control signals in and out of the inverter are disconnected preventing the inverter of triggering a Short Circuit Fault causing K12 to close. Other Faults could still cause K12 to close.

Lacking the battery charger will NOT cause any faults. However without the battery installed you'll need a good 24 volt battery or two 12 volt batteries in series installed to run the generator.
You cannot run the generator and make power with both the charger and batteries missing.

 

[DD58]

If you unplug all 3 white connectors from the inverter the inverter will be disconnected except for it's 3 output terminals.
At that point the inverter will not be receiving any power from the PMA and all the control signals in and out of the inverter are disconnected preventing the inverter of triggering a Short Circuit Fault causing K12 to close. Other Faults could still cause K12 to close.

Lacking the battery charger will NOT cause any faults. However without the battery installed you'll need a good 24 volt battery or two 12 volt batteries in series installed to run the generator.
You cannot run the generator and make power with both the charger and batteries missing.

That’s good to know. So if the invert is causing the fault then that will eliminate the k12 led. If not then something else causing the fault. I have 2 12volt batteries in series right now to run it on. Once this rain stops I’ll bull it back outside and try that. Is there anything else I should test while I have it running?


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[kloppk]

At some point you'll want to verify the Governor Controller is operating properly.
The -13&P TM for the set has the adjustment procedure.
Without the inverter connected you may want to verify that the governor controls the engine speed to the no load speed of 3,050 RPM. RPM can be verified my measuring the AC frequency across terminals A & B of the Governor Controller. At 3,050 RPM you should measure 254 Hz across the terminals.

 

[DD58]

Ok I’ll check that as well and post my findings. Thanks for the help!!!


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[DD58]

Hey guys got a lot done on the gen set. So I got in touch with Dewie38 and he ended up stopping by today. Changed the inverter was the first thing we did. Started the gen set up was making power but the set was surging. Also the k12 led went out once the new inverter was installed. So that tells me something in the invert itself was faulting the set.

to fix the surging issue Dewie38 brought a new governor controller. Changed that out and whammm!! There yeah go purring like a kitten. No more surging. I mean what a nice thing to hear. Got alot of good info and pointers for Dewie38 and great parts!!
Thanks to kloppk for sending me to the forum and getting me in touch with Dewie38. again Dewie38 thanks for all the help today it’s greatly appreciated.

I definitely will be watching the forum to learn more and help out. Oh and one of these days while the wife away I might just get my hands on a Stewart and Stevenson m1078a1 to post up on here.

 

[Guyfang]

Thats what the SS forum is all about. People helping people.

 

[cozmike]

Interesting thread...can you put me in touch with Dewey38?

 

[Guyfang]

He is in the forum. Look his name up and PM him. Or open up a thread.