MEP-804A was running fine and now starts but dies immediately

[smurph]

Well, my trust MEP-804A quit on me. The last time I ran the generator, I set it to 50Hz. I was just using it to power the A/C in my M934. So I fired the genset up this Friday and it ran fine at ~50Hz. Then I decided to switch it back to 60Hz because it was ARRL Field Day weekend and some power supplies don't like 50Hz. So I stopped the genset, switched to 60Hz, and the genset never started again. Well, it would crank over, start, run for about 1 second, and then shut off.

So I read up as much as I could. I followed the TM troubleshooting sections and everything looks good (or it said to notify next higher maintenance level). I read about the MPU issues and I tested that (2.78vac when cranking with dead crank switch). I took the MPU out to inspect it and it looked perfect. I re-installed it and adjusted it to get back to 2.75v. The only thing of note is when the engine fires up and runs for a second and then shuts down, the under voltage indicator light is on. I don't know if that is just a symptom or a problem. But I do see the voltage climb on the meter so I think it is flashing the field coils.

Again, everything was fine when I first fired it up. The frequency was off a little bit and I adjusted the frequency knob to try and set it. But the frequency adjustment wasn't smooth. It jumped from 49Hz to 52Hz, etc.. when I was trying to set it dead on 50Hz. I had a devil of a time getting it to dead on 50Hz. Then I shut it down and switched from 50Hz to 60Hz. That is the only two controls I touched other than the main S1 switch.

I checked the 50/60Hz switch and it is doing the needful. But I didn't check the frequency pot yet. Could that pot cause the electronic governor to just never keep the engine running?

So I guess I'm "notifying the next higher maintenance level" here and asking for help. Anything would be appreciated.

Steve

 

[Evvy Fesler]

Greetings!
Couple of questions.
Did you adjust the frequency under a load?
Did you change it from 50 to 60 (vice versa) while running?

Evvy-

 

[smurph]

I never switch the 50/60Hz switch while running (plenty of warnings about that). And there is no load on the genset.

And today, it is worse. It will not crank over with S1. Dead crank in normal, E-stop good (power on the panel), and when I turn S1 to start, all it does is click a relay somewhere. My guess is K15. K2 works fine with the dead crank switch. Ugh... I guess I need to pull S1 out and test it.

I tested R2 Frequency adjust pot and it indeed has a dead spot. But it reads within spec most places. I ordered a replacement.

I think I will go over the whole panel with Deoxit and re-seat the relays. Because it seems that there are magic gremlins that are all appearing at once. I just don't get why all of this just happens all of a sudden when it has been so reliable in the past. I'm hoping one Mr. S1 is the culprit at the moment.

Steve