Onan 20kw generator control module electrical problems

[Dune]

1993 vintage MDL4 model. Main problem was the "on/off" red rocker would trip the instant I positioned the black rocker in either preheat or start modes. I finally traced the problem to a short in the start relay solenoid. (part 307-1031)

Replaced that, and now preheat and starter work but the gauges are not working and the injection pump solenoid is not getting 12 volts to open. Have checked wire connections carefully so now all I can figure is something on the engine monitor PCB board has gone bad.

Replacement not all that expensive at $160 or so, but will be a major PITA to remove and transfer the wires to a new board.....so before I do that, any other ideas of what to check ?

DC breaker and sensor overload breaker have continuity, so not one of those. The engine temp gauge doesn't work but the generator ran fine before with it not working before these problems occurred so unlikely to be that....but I wonder.

 

[caltexflanc]

Gauge is separate from shut down sensor. I had one of these gensets on my old Hatteras, but never your issue. I may have a manual in electronic form around somewhere. A lot of guys with this unit on Hatteras Owners Forum. You could also try the guys at Flight Systems (who have control boards) and get their advice, usually pretty square shooters.

 

[Alaskan Sea-Duction]

There is a relay within the circuit board. Does it start?

 

[Dune]

There is a relay within the circuit board. Does it start?

Do you mean the clear "ice cube" one or one of the smaller black relays ? On machine tools those ice cube types are always plugged into a socket so slightly annoying this one is soldered on, as otherwise I could simply switch it with a known good one to see.

I guess the theory is the plug in type might vibrate loose on a generator but they typically fit so tight in their sockets I doubt that would be an issue really.

Flight Systems tech said it is probably a bad relay on the board but asking them might be a bit like asking an auto transmission shop about a noise that may or may not be coming from your car transmission !

Regardless I went ahead and ordered a new board from them.... they are not the cheapest on that board but figured if that turns out to NOT be the problem maybe they would be best to guide me what else to look for.

 

[Alaskan Sea-Duction]

Do you mean the clear "ice cube" one or one of the smaller black relays ? On machine tools those ice cube types are always plugged into a socket so slightly annoying this one is soldered on, as otherwise I could simply switch it with a known good one to see.

I guess the theory is the plug in type might vibrate loose on a generator but they typically fit so tight in their sockets I doubt that would be an issue really.

Flight Systems tech said it is probably a bad relay on the board but asking them might be a bit like asking an auto transmission shop about a noise that may or may not be coming from your car transmission !

Regardless I went ahead and ordered a new board from them.... they are not the cheapest on that board but figured if that turns out to NOT be the problem maybe they would be best to guide me what else to look for.

The circuit board itself has a relay. Did you call the Cummins/Onan customer service? They will help you troubleshoot your unit. They have helped me when I get stuck.

(812) 373-5873

Make sure you have the model and spec numbers.

I also buy all my Onan parts from here. You may have to wait a few weeks but they beat Cummins parts.

https://www.jackssmallengines.com/

 

[Dune]

The circuit board itself has a relay.

Right, that's what I'm talking about...but it has more than one...there is a small black one on the board hidden from view under the start solenoid. But more likely it is the clear enclosure larger one you are talking about.

https://www.flightsystems.com/mm5/graphics/00000001/56-2604.jpg


Both relays are so inexpensive I probably could have just replaced those, but to do so would involve removing all the wires and the board just to get to the backside for desoldering and resoldering in new....but the main expense is my labor to remove the board and re connect all the wires so figure I might as well replace the whole thing while at it.

 

[Alaskan Sea-Duction]

That looks like it if my memory serves correctly....