Rooftop AC will not run on Genset but will on shore power. Help!!!

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cw101

Member
Joined
May 4, 2017
Posts
9
Hello,
I have recently purchase a Jayco Octane toy hauler with a Onan 4000 Microquiet.  After purchase I was trying to run generator and after a few minutes it would shut off and give an error code 14.(high frequency?)  I hooked up my meter and it was reading high at 64-66hz.  I adjusted what I think is the governor screw and it lowered the hz down to 60-62 but now my A/C will not run off the genset.  I pluged into outlet in the shop and the A/C fires right up and blows cold.  I have tried the fridge and lights and they work off the generator power.  Have I done something to not let the A/C run off the Onan?
Any help would be appreciated.
 
What is the voltage output from the generator?  If below about 105vac, the A/C may not start up and if it does, may get damaged.
 
Volts were 120-122 and 60-62 Hz, without any load. I checked the breaker beside the start switch on the generator.  Is there another one somewhere else on the 4000?
 
yes I'm checking it at a plug that's on the exterior beside the generator
 
Does the a/c even try to start? It may be that the voltage drops too far hen the compressor tries to start. You should hear a "grunt" as the compressor loads up and then quits due to low voltage. Lights don't put much load on the genset, so voltage stays up.

Put a meter on an outlet and watch the voltage level as you try the a/c.

Does the coach have an auto-transfer switch or do you plug the shore cord into a generator outlet?
 
the camper has an auto transfer switch.  I hooked up a meter on the inside and when I flipped the a/c on it pulled down to around 6 amps and then like the a/c quit trying to start and jumped back to 120.  Although one time while flipping the fan on an then trying to flip to cool, I did get it to run.  Is there some type of booster on the ac to help it get going on start-up?
 
Yes, the a/c has a "hard start" capacitor that gives it a start-up boost. But did the a/c work ok before you had the genset problem?

when I flipped the a/c on it pulled down to around 6 amps and then like the a/c quit trying to start and jumped back to 120.

Is that 6 volts rather than amps? If the voltage falls to 6, that would explain why the a/c can't start.
 
yes 6v not amps. I wrote that too early this morning.  I haven't had the camper but just 3-4 weeks and I have just now been trying to start it off the genset.
 
Molaker said:
Do you have AC at the outlets in the RV?

cw101 said:
yes I'm checking it at a plug that's on the exterior beside the generator

cw101
Is the curcuit breaker for the roof A/C unit in the 120VAC electric panel in your RV tripped?

BTW checking for 120VAC "at a plug that's on the exterior beside the generator" may not tell you anything about the generator power IN the RV.
On my coach the 120VAC from the generator goes "directly to" the receptacle beside the generator, (without passing through the transfer switch).... but before the 120VAC generator power goes into my coach it "passes through the transfer switch".

 
Does sound like low voltage to me as well..

USUALLY Onan puts 2 breakers on a generator for RV use. on a 30 amp RV one will be 30 amp and the other 20, the 20 is for one Air Conditioner.  The 30 the rest of the house.

BUT... the key word is USUALLY.  Appears you have but one.

I'd check all wiring.

Oh, and on 30 amp RV's the transfer switch does a few convulted things so check it too.
 
checked voltage on the interior plugs as well and it was 120.  All the breakers are on also.
 
Never seen a 4000 with more than one breaker. Did the AC run from the generator before you made the adjustment?
 
Many generator heads are actually 2 separate generators inside. A generator that runs at 1,800 RPM is just one. A generator that runs at 3,600 RPM is actually 2 inside split in half. They normally split them up into 2 20amp circuits or tie them together for one 30 amp. If yours is the two sided generator you can have one side go bad. Then your 4,000 watt is a 2,000 watt and will not run the AC. That's what it sounds like to me.
 
cw101 said:
checked voltage on the interior plugs as well and it was 120.  All the breakers are on also.

cw101
I suggest you next verify that you are getting 120V generator power at the A/C end of the wires to the roof A/C unit.
If you are the problem has to be in the A/C unit itself.
 
Try plugging some other high-amp appliance, e.g. an electric space heater, and see how the genset handles that. It begins to appear you have a genset problem.
 
Ok, so I have replaced my hard start capacitor that was already on the a/c today and I think it has solved my problem.  Now I have a somewhat new problem that I thought I had remedied but when I turn on my ac now and the generator goes under load it does fine and runs like a champ.  When I turn it off and there is no load on the generator it revs up and over frequency faults again.  I had the htz right at 60 without load yesterday when I was running it.  Can there be an adjustment out of whack on the genset ?
 
cw101 said:
Ok, so I have replaced my hard start capacitor that was already on the a/c today and I think it has solved my problem.  Now I have a somewhat new problem that I thought I had remedied but when I turn on my ac now and the generator goes under load it does fine and runs like a champ.  When I turn it off and there is no load on the generator it revs up and over frequency faults again.  I had the htz right at 60 without load yesterday when I was running it.  Can there be an adjustment out of whack on the genset ?
Probably the one you messed with to start with.
 

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