MEP802 short circuit?

[CDR]

Oh here it goes... Been through everything with this MEP 802. Now I'm getting my short circuit light staying on. The motor doesn't even have to be running. Regardless the light is on if you close the breaker to get 220 V to the house. The second you try putting a heavy load on it the breaker will open. It never did this before the only thing that changes I washed it which I'm assuming water could've touch something. Don't even have a clue where to start looking as anyone had an issue with this?

And on a serious note after I spend 20 hours of my life figuring this new problem out I'm done with this... These generator may be quiet but there not even close to as reliable as the mep002. Me and this generator have never got along from day one. If anyone's interested in my generator for what I have into it PM me

 

[leedawg]

Wow that bad eh, makes me wonder if I should think twice about fixing the 803 I got, my 003 runs great. I look forward to tracking this problem though with ya.

 

[m-35tom]

well, if you spray electrics with water you may get problems. pull the top cover gen end and blow everything dry. the dust that comes in many of these is a good insulator when dry, but when wet who knows. i literally pull both top covers and pressure wash everything and then blow dry and have not had any problem with 13 of these. the 802 is a far better machine than a 002 ever was.

 

[CDR]

What exactly do the ballast resistors do? I noticed that one wire sodier joint was lose on the top one. I haven't had a chance to sodier the connection yet wondering if that's part of my problem.

The other thing I was thinking I know another member on here showed pictures of wires chafing wondering if one of my wires chafed threw..

 

[CDR]

 

[rustystud]

well, if you spray electrics with water you may get problems. pull the top cover gen end and blow everything dry. the dust that comes in many of these is a good insulator when dry, but when wet who knows. i literally pull both top covers and pressure wash everything and then blow dry and have not had any problem with 13 of these. the 802 is a far better machine than a 002 ever was.

I don't know if I would go that far about the MEP-002A. I have talked with a old ONAN mechanic, who ran the ONAN rebuild center in Seattle. With just the bare minimum of maintenance these engines would last for years under severe use. Yes it is loud, and yes it vibrates like crazy, but they last and last. Someday I would like to own a 802, but until then my trusty old MEP-002A will just keep on going.

 

[m-35tom]

View attachment 523256

these provide load for the current sensing transformer so the load circuit knows the load.

 

[Crabbie]

What you are seeing is a pretty common problem with the 800 series gen sets when they get wet. Put a fan on it for a couple of days to dry it out, many times they will fix themselves when they dry out. Good luck.

 

[Ratch]

While not meaning to contradict anyone here, I've powerwashed mine and let it sit out in severe weather running the house and it's still pretty happy. I'm talking exterior, though I'm pretty sure I also hosed out the back of the control board and cavity unintentionally.

There was a service bulletin issued about some wiring to the main contactor rubbing through from vibration. I believe it was considered urgent, but for the life of me, I have not been able to find those documents that detailed it again.

If you suspect a wire is worn through, follow every one from the Gen head, then the contactor, to the lugs.

I assume you already check for anything obvious, like a piece of wire vibrated off it's position, or bare metal or wire laying across two contact points.

Whatever you do, make sure the chassis is grounded before you touch this thing while it's running.

 

[Crabbie]

All true Ratch, but if you get water in the generator end it self the short light will commonly come on. It expected that these units will set out in the weather unprotected, that is what they are designed to do.

 

[CDR]

Okay so I spent two hours on it today just turning the switch on never even started the motor the short-circuit light is still on. Checking every wire and every connection the main feeds from the generator head are definitely worn but not exposed. In the middle of playing everything I burnt my hand on a generator that wasn't running???
For some reason CR-1 which is the diode is red-hot. I can't find it anywhere on the schematic. I've never heard of a diode going bad but is it possible that it went bad and it shorted?

 

[CDR]

everyone for their help trying to solve this

 

[212sparky]

What was the fix? The bad diode?

 

[glassk]

PUSH TEST RESET LAMPS Tests and resets fault indicator lamps.

 

[CDR]

PUSH TEST RESET LAMPS Tests and resets fault indicator lamps.

I did that and I highly doubt that would help my Diode from glowing red

 

[CDR]

What was the fix? The bad diode?

Not fixed yet

 

[Ratch]

Diodes can definitely fail shorted, but they usually fail open. Remove battery power asap, and replace that diode. I don't know if it will solve your problem, but that is probably not designed to do that...

There could also be some current limiting device further down the dc circuit allowing too much current to flow through the diode, but I've typically seen diodes blow up or open when they over current in forward bias. What you could have is a reverse bias breakdown in the diode, causing a direct short that's shunting low resistance (resistance from other circuit components) dc battery current. While it is a short, it's not one I'd expect a warning light for, but I'm not looking at what that diode is doing. You only have dc battery power present with the machine not running, though, so it has to be somewhere in the battery circuit.

 

[Ratch]

All true Ratch, but if you get water in the generator end it self the short light will commonly come on. It expected that these units will set out in the weather unprotected, that is what they are designed to do.

sheesh, how the heck do you get the head wet? That thing is pretty well protected. But that would make sense.

 

[glassk]

I did that and I highly doubt that would help my Diode from glowing red

But troubleshooting the short circuit relay by the TM probably would

 

[m-35tom]

CR1 is just there to prevent you from installing batteries backwards, otherwise you don't need it. but, you have other problems. power from battery goes to CR1, thru it to the throw of the dead crank switch, then when normal pos to the emerg stop switch, thru that to CB1 and then on to power the DC circuits. so if CR1 gets hot from to much current why does CB1 not trip? it is 7 1/2 amp. the only good answer is it is bad or there is a short before it gets to CB1. push the stop switch and see if there is a problem then, if not it is after it and CB1 must be bad.