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tropical36's avatar
tropical36
Explorer
Jul 12, 2016

Onan 7.5 Diesel Generator problem

OK, here we go again with this new to us coach.
I go to start the genset today and nothing but the preheat and fuel pump is working. Starter won't turn over at all.
Fault code 46 present and says that it's low battery voltage, but batteries are up and can read it from down under where it comes in to the genset.
Only low voltage was from the junk batteries that the dealer stuck me with, when purchased a few weeks ago, so don't know if fault code is an old one or not. Thing is, there's plenty of power there now, with 4 AGM's supplying it.
It was running when I picked it up and stayed running for a good 4 hours and until I shut it down, when arriving home, two weeks ago.

Anyway, I'm out of ideas and want to blame it on a bad starter. At the same time, don't want to start ripping things apart if I'm just missing something here. So, if anyone has any suggestions, I appreciate hearing them, before getting on the phone tomorrow and possibly making an appointment with Cummins.
Class A

7 Replies

  • tropical36's avatar
    tropical36
    Explorer
    Jul 13, 2016
    melton wrote:
    You may want to consider changing the generator to start on the chassis batteries, along with the engine, instead of on the house batteries. If the house batteries become depleted, such as when dry camping, they may not be able to start the generator. Also, the chassis batteries are better designed for the short burst of high current needed to start either engine.

    That's a thought, but have never had a problem with the old coach on house power. Could always start the engine for instant power if the aux boost didn't want to work.
    As for starting power, I put in 4 Group 27 AGM's like it came from the factory and according to Fleetwood's recommendation and expect they will crank over the big Cat as well. Whether or not 6v or some other type would have been better, I'm not sure at this point and just wanted it back like original. I did negotiate a pretty good price for these and hope they will serve us well all around....
    Batteries Plus
  • melton's avatar
    melton
    Explorer
    Jul 13, 2016
    You may want to consider changing the generator to start on the chassis batteries, along with the engine, instead of on the house batteries. If the house batteries become depleted, such as when dry camping, they may not be able to start the generator. Also, the chassis batteries are better designed for the short burst of high current needed to start either engine.
  • tropical36's avatar
    tropical36
    Explorer
    Jul 13, 2016
    11178adm wrote:
    check the voltage at the gen set starter solenoid or if it has one the relay that activates the solenoid. should be 12 volts, also check the voltage at the trigger post when trying to start the gen set does it start with the override that connects it with the house batteries? also my 94 am eagle has it's own battery and alternator.

    Problem solved above, but good to know and did try the aux. boost along the way.
    Interesting that your Eagle has it's own of everything. What brand of gen set is it?
  • 11178adm's avatar
    11178adm
    Explorer
    Jul 13, 2016
    check the voltage at the gen set starter solenoid or if it has one the relay that activates the solenoid. should be 12 volts, also check the voltage at the trigger post when trying to start the gen set does it start with the override that connects it with the house batteries? also my 94 am eagle has it's own battery and alternator.
  • tropical36's avatar
    tropical36
    Explorer
    Jul 13, 2016
    Poor dumb OP here with an update and do I have a lot to learn about Diesels, beginning with the basics. I didn't realize that it might take a whole 15 seconds of preheating, before the gen set would start and who would have thought, down here in the tropics and in summer, at that. I mean the main engine doesn't act like that, but do realize that it has a block heater for when in cold climates. It must have take at least 11 secs to start, but hey, I'm happy now, as it sounds good and has good power.
    Hope all this aggravation might have helped some other Diesel newbie. Otherwise, sorry for wasting the ink.
  • tropical36's avatar
    tropical36
    Explorer
    Jul 12, 2016
    2chiefsRus wrote:
    are you sure it is powered by the 4 house batteries and not the chassis batteries? How are the chassis batteries?

    Shut off the house batteries to be sure, so yes it's house powered.
    Chassis batteries are up as well and did start the engine to make sure it would start. Cranked over very strong and started immediately.
  • 2chiefsRus's avatar
    2chiefsRus
    Explorer
    Jul 12, 2016
    are you sure it is powered by the 4 house batteries and not the chassis batteries? How are the chassis batteries?

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