MEP-804a internal generator wiring on high Voltage setting

[jkauto384]

Genset MEP-804a (2006) is running OK with low voltage setting. If is set to high voltage (TB1 board in up position) almost immediately RPM will drop very low and short circuit light is illuminated. I suspect internal wiring short in generator (G1) There are 12 wires coming out of G1. is there electrical wiring diagram of internal G1 connections?

 

[Scoobyshep]

10 leads for power and 2 field.

Need to check the terminal points and make sure they are going to the right places. Do you have a megger?

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[Guyfang]

Take the four standoff studs out. Pull the board forward and check each and every wire/connection on the board.

To add to Scooby's post, open up the -24 TM and read at least twice how to check the Main gen. If you don't have a megger, borrow one. Its not rocket science.

 

[jkauto384]

10 leads for power and 2 field.

Need to check the terminal points and make sure they are going to the right places. Do you have a megger?

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No I do not have a megger . I will check all terminal points for correct position. This is hard short so you may be right about connections.

 

[Scoobyshep]

No I do not have a megger . I will check all terminal points for correct position. This is hard short so you may be right about connections.

What has me thinking it's a connection issue is it only manifests in high mode can you confirm that it works correctly in the low position?

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[jkauto384]

Take the four standoff studs out. Pull the board forward and check each and every wire/connection on the board.

To add to Scooby's post, open up the -24 TM and read at least twice how to check the Main gen. If you don't have a megger, borrow one. Its not rocket science.

I'm getting one. And I did that. All wire position on TB1 are OK. I'm curios how G1 leads T1 to T10 are internally connected ?

 

[Scoobyshep]

I'm getting one. And I did that. All wire position on TB1 are OK. I'm curios how G1 leads T1 to T10 are internally connected ?

Attached is a low and high tap diagram. Shown here is t10 t11 t12. These are internally tapped together and come out to become l0.

The following are the ends of windings:
1 to 4
2 to 5
3 to 6
7 to 10
8 to 11
9 to 12
In your case you should have continuity from 7 to 8 to 9 to neutral , 1 to 4 2 to 5 and 3 to 6.

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[Scoobyshep]

Helps if the photo actually loads.

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[jkauto384]

Thanks, Scoobyshep and Guyfang, you both hit a nail in the head. This one is fixed and purring like a cat. The problem was that as someone went there before and they switched position lead T0 to T4. The was no tags on some of the leads so it took me some time to figure it out. But this was not the only mix up. Main switch in GLOW PLUG position would activate aux fuel pump and accordingly in RUN/AUX FUEL PUMP will switch on glow plug relay.
Thanks again.

 

[jkauto384]

Great, i wish i could have this diagram. I will save it just in case. Thank you.

 

[Guyfang]

Normally when I hear that it works in low voltage and not in High voltage, Its a wire in the wrong place. In the military, 95% of the gen sets run only in low voltage mode. So the problem never raises its ugly head.

 

[Scoobyshep]

It's a really bad place to have a wiring fault. There's no protection there. The only way to stop the unregulated angry pixies is to dump the field, stop the engine, or on really bad shorts it will stop the engine for you. The other thing to think about is one leg wasn't getting the right current balancing so the capacity was potentially reduced.

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[LuckeyD]

Hello Folks. New to all this but worked the equipment for 47 years and was the ARMY's SME for a few of these. Guyfang asked me to get involved. All works at 120/208, but immediate short at 240/416. Main gen is OK if it still works on low voltage. That board just takes a parallel strapping and makes it all serial. Regulator is also good if it still works on low voltage. Step 1 as Guyfang and scooby stated is check each wire behind the reconnect board. Use wire numbers from the 24 manual schematics. Yell if you don't have. Some are still on the doors of the gen. Here is one they did not say; Once you get the wiring right, as it is not, now comes the pain. Remove the load terminal board retaining bolts and nuts and tilt it forward. You can also see some if the rear pannel is removed. You will also find block looking usually white filters and rather large wafer caps. Inspect for any burn marks. It does work for utility power if something there is missing, hint. Let us know what you find

 

[Guyfang]

Greetings Mr Lucky!