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Author Topic: 1992 Onan 4000 Generator challenge  (Read 564 times)

B737doc

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  • Posts: 71
  • 1992 Challenger
1992 Onan 4000 Generator challenge
« on: November 28, 2017, 07:34:49 PM »
1992 Damon Challenger Motor Coach.  Onan 4000 Generator using two 12 vdc batteries wired in parallel (they share a common ground, but 2 different wires coming off positive posts).  Removed the batteries for winter storage in my garage and placing them on a trickle charge.  Installed batteries in order to start generator, relay clicked a few times, then nothing. I checked voltage at the relay and was reading same as battery voltage (13+ vdc).   Jumped relay, still nothing, not even a click now.  Started main engine, selected house switch to the "ON" position, generator started right up. Selected house switch to "OFF" position, generator dies. Re-configured to previous condition, generator started up again.  Left in this condition for 10 minutes then selected house switch "OFF" and generator continued to run for 20 seconds, then cut off. I don't see how one of those batteries are THAT dead all of a sudden, and showing 13+vdc....but that's really all that makes sense.
1976 BMW R90/6 "Airhead"
2005 Triumph Bonneville "America"
1992 Challenger Motorcoach

Old_Crow

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  • Posts: 720
  • Former Phantom Fixer
Re: 1992 Onan 4000 Generator challenge
« Reply #1 on: November 29, 2017, 06:28:54 AM »
0n both the coaches I've owned, the generator starts off the house batteries.  If the house battery disconnect switch is in the "off" position, you won't have any battery power to the generator's starter motor so it won't start. 
I've never turned the battery switches off while the generator was running, so I don't know if it should die when battery power is lost or not.
Wally Crow
Retired 30 year ASE Master Auto Tech
Y2K Bounder 36S F53
'03 Jeep Wrangler Sahara

Ernie n Tara

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  • Life is Good - Together
Re: 1992 Onan 4000 Generator challenge
« Reply #2 on: November 29, 2017, 09:09:53 AM »
The generator also gets its 12V power from the house battery (it does not have its own battery).

Ernie
Ernie 'n Tara

2011 Winn Journey 34y
2012 Jeep Rubicon - Dozer (orange - kinda)
2006 Jeep Wrangler

B737doc

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  • Posts: 71
  • 1992 Challenger
Re: 1992 Onan 4000 Generator challenge
« Reply #3 on: November 29, 2017, 05:04:46 PM »
The generator ALWAYS ran regardless of the switch position.....until now.   Suspect house battery.  Allowed Generator to run for half an hour, switched off house battery switch, and generator stayed running for 30 seconds, then died.  I did put the old starter that I replaced from the generator in a vice and both batteries spun it over very healthy, but the starter wasn't turning an engine either...need to take to autozone and load test both batteries.
1976 BMW R90/6 "Airhead"
2005 Triumph Bonneville "America"
1992 Challenger Motorcoach

Charlie 5320

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  • Posts: 2102
Re: 1992 Onan 4000 Generator challenge
« Reply #4 on: November 29, 2017, 07:44:00 PM »
Depends on IF your generator has battery charging  capabilitys or not. Some onans do some do not. If it does NOT, the generator has to have 12 volts for it to run. So when you turn off the battery you are cutting the power to the control board on the generator, thus shutting it down. Why would you be shutting the battery off when the generator is running? Don't make any sense, you can't replace the amps you used starting the generator, if it is turned off. 

If it did run in either position before, you may have a bad rectifier on the generator. Best to look on the schematic for your generator to verify it does have a battery charging circuit before looking for other problems.

I just checked and both the bge and the microlite do have battery charging circuits and should produce 12 volts. They both use resisters to accomplish this though, and could be defective.  Theses circuits are only designed to replenish the voltage used in starting the generator and will not charged a dead battery. 
« Last Edit: November 29, 2017, 08:14:39 PM by Charlie 5320 »
2003 National Dolphin 5320
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98 Damon Daybreak 3130
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skydivemark

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  • Posts: 72
Re: 1992 Onan 4000 Generator challenge
« Reply #5 on: December 01, 2017, 09:30:20 AM »
It's possible when you turn the battery switch off the fuel pump quits running and then it just uses the fuel remaining in the float bowl,  20-30 seconds.
2015 Thor Four Winds 31L
Clermont, FL

B737doc

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  • Posts: 71
  • 1992 Challenger
Re: 1992 Onan 4000 Generator challenge
« Reply #6 on: January 24, 2018, 03:31:23 PM »
    Took the batteries out for winter protection, re-installed both batteries, and generator starts fine.  Was definitely a bad connection on the battery.
1976 BMW R90/6 "Airhead"
2005 Triumph Bonneville "America"
1992 Challenger Motorcoach