Forum Discussion

MobileBasset's avatar
MobileBasset
Explorer
Jul 19, 2015

Onan generator is turning itself on

It's an Onan 4000 gas generator. I ran it earlier today at a rest stop to power the AC.
When I arrived at our overnight I tried to turn it on again for the AC while I checked in ( for the dogs) but got nothing from the remote starter. No sound.
While setting up we had a massive rain/lighting storm and my surge guard got hit and went out. I checked the power post with a meter and it looked OK so I connected the RV to shore power.
Then I looked at the generator. The on-unit switch was glowing red and a very low rumbling was going on. I can fool with the switch, push it around and get it to start up and run normally and get it to turn off for a little while but the switch slips back into this semi-ON position enough to get the low rumble. With the cover in place it will sometimes sound more rat-a-tatty.
I can't get anyone to look at it until at least tomorrow or Tuesday and I am worried about where it is getting the power to rumble. I have not disconnected the house battery (disconnect switch). Don't know if that will help or hurt. If I ignore it will it drain my engine battery?
Class C
  • DrewE's avatar
    DrewE
    Explorer II
    Jul 20, 2015
    I should probably have been more clear. There is a 30A circuit breaker on the generator that only shuts off the output; it doesn't stop the generator engine from starting or running.

    At least on mine, there's also an automotive style twin-blade fuse for the 12V control circuitry, of 5A or so capacity (off the top of my head). I think pulling that would prevent the generator from starting due to bad controls etc.

    It's all rather academic now, though, since it sounds as though the generator is working properly now and none the worse for any wear.
  • dicknellen's avatar
    dicknellen
    Explorer II
    Jul 20, 2015
    The circuit breaker you switched off will only stop the gen from sending out 110v power, I don't think it will stop it from starting. Dick
  • Snowman9000's avatar
    Snowman9000
    Explorer
    Jul 20, 2015
    Ours was starting by itself, or just clicking the starter relay repeatedly. The dealer diagnosed it as a faulty remote switch. Since they replaced it, the problem has stayed away.
  • MobileBasset's avatar
    MobileBasset
    Explorer
    Jul 20, 2015
    I pushed around in the cable harness in the left compartment trying to sort out which was the battery cable connection. I was thinking I would disconnect it. While I was pushing the cables the rumbling, which had morphed into what sounds like a starter clicking, stopped and the switch light stayed off. Then, on DrewE's suggestion, I found what the manual calls a circuit breaker and flipped it. It is a tiny little flip switch. So far so good for the past 20 minutes.
    I know nothing so trying to sort out the remote cable is probably beyond me. It's not labeled in the manual.
  • DrewE's avatar
    DrewE
    Explorer II
    Jul 19, 2015
    You could also pull the fuse on the generator itself (the little 5A fuse); I think this will disable the controls and prevent the starter solenoid etc. from kicking in.

    The generator may well be connected around the disconnect switch as it doesn't generally pose any parasitic loads when it isn't running and because it requires a hefty amount of current when cranking. I know mine is.

    The low rumbling you hear—is that the fuel pump in the generator priming the carburetor? That would suggest that a switch is sticking in the "shut off" position rather than the proper "neutral" position.
  • enblethen's avatar
    enblethen
    Nomad
    Jul 19, 2015
    Go to genset compartment and disconnect the remote control cable. If the remote switch is bad that could solve issue for now.
    You can still operate the genset from the unit itself.

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