This is for all of you smarter than me (lots of you, just ask the DW) Onan and A/C people. I had an earlier thread but the transfer switch repair has changed the issue some so I am starting a new thread.
I have a 2000 Monaco Windsor motorhome with an Onan 7.5HDKAJ11451F generator (62.5 amp output) (726.5 hours) and two DuoTherm13,500btu model 620315.321 airconditioners with 1530btu heat strips. Single four button DuoThrem comfortcontrol thermostat.
THE PROBLEM, when I turn on either a/c unit (nothing else at all running in the rig) the generator instantly dies (error code 3 sub cat 11) whenever Either a/c compressor even thinks about coming on. No breakers or fuses ever blow on the generator, rig or a/c units.
THE HEAD SCRATCHING PART, here are the tests that have been done:
1) the generator was just serviced. Oil changed with new filter, all levels checked, new fuel filter and air filter. Fuel tank is full of fresh diesel.
2) the generator will, at the same time, run both duotherms with heat strips on, the battery charger/inverter, the electric hot water heater and the microwave. Total amperage draw 54 amps (38 line one, 16 line two) with no problems. If I add the coffee pot (additional 12 amp load, 66 total amps) the generator quits
(As expected) with the same 3-11 error code.
3) on shore power, The front a/c draws 18amp max load when the a/c compressor kicks in and then draws 12amp while running. The rear A/C draws 13 running and 19 spike.
4) I installed OEM Duo Therm hard start kits with electrionic relays designed for these a/c units on both a/c's. that means the start capacitors are new and the ceramic PTAC are replaced with relays. The run capacitors test in spec.
5) both compressors test good. The scratch test shows no continuity to case from any terminal. There is continuity between all start/run/common terminals. The ohm test on the compressor are C-S 7.2Ohm C-R .7 Ohm S-R 7.9 OHM
6) on shore power both a/c units start and cool properly with no issues.
7) As stated before, the fan and heat strips on both units run without issue on the generator. It is only the cool mode that is an issue.
The generator operates properly with a 54 amp load. The A/c compressors test ok. Both a/c units work /cool properly on shore power. The max power amp draw on the a/c is not excessive and is well within the power produced by the generator using other loads. Both a/c units act exactly the same so if it is an issue it is the same issue on both units.
Any Thought or ideas????? Is there anything in the a/c circuit boards or thermostat circuit that could cause this issue?