Onan won't stop.

[tsawyer]

Ok, gave the genset a start this AM just to let it run a bit.

I hit the switch to shut it down and it won't shut down. So I went to the switch on the genset and it too won't shut it down.

I pulled one battery cable off and it shut down.

So, is this a ground problem? Should that be somewhere between the genset and main battery?

Thx

Tom

[Big D]

There may be a stop relay in the circuit, it has probably failed. If you're good with a test meter, you can dsiagnose to see if that is indeed the problem.

[g36]

not knowing which onan you have i will assume its a mcck like most of us have. yes there is a stop relay k4. the below link has the mcck lsiting along with others look at page 3-9 figure 3-5 and also page 4-5 figure 4-2 this will give you the info and apx location for it. they arent really that expensive either. if this isnt your model gen then it may be slightly different. instead of pulling the battery cable you could have turned off the fuel supply to the gen if there is one, or the safety low oil pressure or overtemp circuit sensors. anyway once it is running again and you can turn it off i would put a meter on the battery with the gen running and see if it still charging the battery. its generally detrimental to the diodes in the charging circuit to remove a battery cable like that but i totally can understand not knowing how to get the generator off and sometimes you have to do what you have to do. just give it a check to see if its still charging
the first link is the manual i referenced and below are a couple others if the model is what you have, for future reference
part can be from internet or your local cummins dealer,
hope this helps

http://www.cumminsonan.com/www/pdf/manuals/900-0196.pdf

http://www.cumminsonan.com/www/pdf/manuals/927-0121.pdf
http://www.cumminsonan.com/www/pdf/manuals/927-0752.pdf

[sluggo]

Ok, gave the genset a start this AM just to let it run a bit.

I hit the switch to shut it down and it won't shut down. So I went to the switch on the genset and it too won't shut it down.

I pulled one battery cable off and it shut down.

So, is this a ground problem? Should that be somewhere between the genset and main battery?

Thx

Tom

I had this happen as well, and was in a panic. turns out the fuse for the remote start/shutoff was gone. I took out all the fuses and it shut down. then I replaced all the fuses , and works like it is supposed to. I have found it easy to bump those fuses out of the genny when fooling around back there.

[tsawyer]

I hooked the battery back up and the fuel pump is running. I removed the fuses and when the middle one is out it stops.

I appreciate the manuals, but still need to figure out which part is my problem. I'm not so good with anything but basic electrical.

I did some searching on smokstak.com and the part may be available at any auto parts store.

Per schematics, It seems to have a start relay and a stop relay. Both should be connected to the start switch. I need to figure out which one is which.

[sluggo]

I hooked the battery back up and the fuel pump is running. I removed the fuses and when the middle one is out it stops.

I appreciate the manuals, but still need to figure out which part is my problem. I'm not so good with anything but basic electrical.

I did some searching on smokstak.com and the part may be available at any auto parts store.

Per schematics, It seems to have a start relay and a stop relay. Both should be connected to the start switch. I need to figure out which one is which.

not to beat a dead horse, but did you check the fuses?? if they are out, it will keep running.

[tsawyer]

I took a quick look at the fuses and they appear ok. When I removed the middle fuse, it quit running the fuel pump.

[Big D]

....I'm not so good with anything but basic electrical....

You could perform some static tests with a meter on the relays but the component fault may only present itself when powered up. Given that you're dealing with a potetially lethal voltage in the circuitry box of the generator while it's running and your comment above, I don't know that it's a good idea to perform this type of testing. In any case, with all generators, make sure that any "Automatic" start-up system is disengaged before you start probing its circuitry.