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-   -   Rear A/C stalls Generator (https://www.irv2.com/forums/f84/rear-a-c-stalls-generator-542353.html)

volvik 06-22-2021 05:26 PM

Rear A/C stalls Generator
 
Situation:

2 x 20a AC units.

Generator on, AC1 (front) on and works no problem. Turn AC2 (rear) on and generator stalls. The generator will stall when AC2 is turned on regardless if AC1 is on or not.

Shore power plugged into a house 15a circuit. AC1 turned on works no problem. AC1 turned off. AC2 turned on and nothing happens at all.

In the morning I will go up on the roof and remove the cover for AC2 to inspect the coils for cleaning.

In the meantime, is it possible that the culprit is the 20a breaker? This is the first test since winterizing in the fall.

Thanks in advance!

windsorbill 06-22-2021 09:32 PM

Quote:

Originally Posted by volvik (Post 5802010)
Situation:

2 x 20a AC units.

Generator on, AC1 (front) on and works no problem. Turn AC2 (rear) on and generator stalls. The generator will stall when AC2 is turned on regardless if AC1 is on or not.

Shore power plugged into a house 15a circuit. AC1 turned on works no problem. AC1 turned off. AC2 turned on and nothing happens at all.

In the morning I will go up on the roof and remove the cover for AC2 to inspect the coils for cleaning.

In the meantime, is it possible that the culprit is the 20a breaker? This is the first test since winterizing in the fall.

Thanks in advance!

Your generator wouldn't stall if the breaker was bad. It would trip the breaker or the breaker wouldn't set at all. See if your motor on the roof will rotate. My first thought is that AC compressor is frozen and not repairable.

Diesel-Lover 06-22-2021 09:32 PM

There are many possibilities and a piece meal checking of the components is called for. If you look at the wiring diagram you may find the circuit breaker is the same one that is handling the load when plugged into the shore power.


If the start capacitors are the issue it may be a good time to also put in a soft start to make every thing work smoothly and reducing the drain jolts on compressor startup. Best of luck and keep us posted.

HarryStone 06-22-2021 10:02 PM

Agreed. You have an AC problem, not a generator issue

MSHappyCampers 06-23-2021 10:44 AM

I would suspect that the A/C compressor is locking up, but I would think it would trip the breaker. :confused:

96 Wideglide 06-23-2021 11:19 AM

Quote:

Originally Posted by windsorbill (Post 5802332)
Your generator wouldn't stall if the breaker was bad. It would trip the breaker or the breaker wouldn't set at all. See if your motor on the roof will rotate. My first thought is that AC compressor is frozen and not repairable.

This sounds like the most likely cause.

If you get on the roof and everything spins freely, may want to look at the capacitors.

jacwjames 06-23-2021 06:07 PM

My front AC was pulling high amps when starting and eventually started to trip the breaker. It was also louder.
So I got on the roof, pulled the cover off and tried to spin the blower motor, could barely move it by hand.

So I bought a new motor for ~$125 ~6 years ago and it replace. One thing I found also was that the rubber isolation pads on the motor were essentially wore out letting the squirrel cage fan hit the metal. The new motor came with new rubber pads.

That fixed the problem, AC runs good and is a lot quieter.

volvik 06-23-2021 06:54 PM

Well I poked around more, read more, tried more all without much success so I'm going to pass this AC issue onto a shop. One additional thing that did happen which may explain the generator stall when I tried to turn that one AC unit.

I tried to start the generator today and it would turn over but not run. When I had a look at the unit I noticed it was giving a fault code......#27. Something about Controller unable to sense output voltage etc and sadly the remedy is to take it to an Onan Service Rep. Now the AC unit should still have worked off the 15a house circuit I'm plugged into as I did try that with the other AC turned off.

I'm hoping that it's an AC unit repair and not replace as so many parts are hard to get during Covid.

The AC unit is an AirXcel which has since been replaced with a Coleman Mach I believe.

Lt Dan 06-23-2021 07:12 PM

I just had the same thing happen with our front A/C. When it tried to start you could hear the generator sort of stall. I watched the power draw and saw a 60 amp pull when it tried to start. The breaker didn't trip as it takes an over amp draw over a longer period. That high of an amperage draw indicates a locked rotor condition and I replaced the unit yesterday.

THenne1713 06-24-2021 07:53 PM

If AC over-amping, it should trip the 20a breaker; if not, maybe breaker contacts welded shut?

96 Wideglide 06-24-2021 08:09 PM

Quote:

Originally Posted by volvik (Post 5803539)

I tried to start the generator today and it would turn over but not run. When I had a look at the unit I noticed it was giving a fault code......#27. Something about Controller unable to sense output voltage etc and sadly the remedy is to take it to an Onan Service Rep.

That could be a bad one like thrown magnets, bad control box, or like when I had a fault code #27, and once I got the top panel off, found a wire connector came apart :dance:!

volvik 06-25-2021 04:21 PM

Ok well I know believe that the generator stalling is a different issue and while Onan fault code 27 suggests a controller issue I now recall 5 years ago I had a similar issue when the generator was under any load it would stall and/or when it was very hot out (like it is now) it would turn over but not run. When I put a new fuel filter in at that time the problem went away. The auto shop will have one for me in the morning so I'll change that then.

Now for the rear AC, I opened the service panel and put a meter lead on AC2 (rear unit) and the neg on the service panel neutral bar. The reading was 3.0v. The breaker is on during this test. When I then test AC1 (front unit) I get a reading of 107.x v.

Oddly enough the water heater only gives me 3.0v as well. The microwave, fridge and general small appliances give the 107v)

The circuit breaker for AC2 is a Murray MP2020. It's a tandem breaker, 20a for the AC and a 20a for a general appliance breaker.

Odd?

THenne1713 06-30-2021 11:14 PM

Cycle Breker, it is half tripped

volvik 07-01-2021 10:23 PM

Nope, already checked that possibility.

However what I have done is taken the wire from that AC circuit breaker in the coach service panel and then started the generator. It started fine and then I turned that AC breaker on and the generator continued to run instead of quitting. I then metered the circuit breaker and it read 120v.

So, the generator is providing power to that circuit breaker which now leads me to believe that the problem is upstream from the circuit breaker ie: from it's power lead from the CB to the AC unit on the roof.

I assume if there's a short somewhere it will cause the generator to die. Odd that the generator CB didn't trip and quit instead.

I have read that a symptom of a bad AC start capacitor is that the unit wont start and could give low voltage. Low voltage is also one of the reasons listed in the Onan fault code 27 I get when it dies.


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