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Hello, I have a camper-top air conditioner that I need help ...

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Hello, I have a camper-top...
Hello, I have a camper-top air conditioner that I need help with. It is supposed to draw around 15 amps of current when running, but it draws much more than that after it has been running for a short while. When I have it plugged into a 50 amp service line, it will run continuously and cool just as it is supposed to. However when I run it using my generator, which has a 25 amp circuit protection breaker, it trips it after about 10 minutes. I can see the power meter spike, but I don't know what is causing that because the compressor is already running. Do you have any idea what faulty component can cause these symptoms?
Submitted: 14 years ago.Category: RV
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Answered in 55 minutes by:
6/23/2008
RV Mechanic: Robert, RV Mechanic replied 14 years ago
Robert
Robert, RV Mechanic
Category: RV
Satisfied Customers: 24,097
Experience: 23 yrs. RV experience including Cummins North West, Country Coach, Monaco Coach - vendor certified.
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Hi There!

Thanks for Choosing Just Answer.

What is the Year, Make and Model of the RV? Who is the manufacturer of the roof a/c and generator?

Thanks, RJ

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Customer reply replied 14 years ago
It's an '86 Fleetwood Tioga on a Ford E350 Chassis. The AC is a BriskAir Duotherm Model # XXXXX I have a Craftsman 3600 Watt generator that is new, but the AC did the same thing with the old 4000 Watt Onan before I removed it from the camper for a tune-up. I haven't put the old generator back in yet...
RV Mechanic: Robert, RV Mechanic replied 14 years ago

OK

Is the compressor cycling on and off?

Thanks.

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Customer reply replied 14 years ago
It seems to be cycling on and off normally. Do you need me to time the frequency? I can do that this evening if you need me to.
RV Mechanic: Robert, RV Mechanic replied 14 years ago

NO

That's OK I wanted to make sure it was cycling on and off. I can give you some ideas, normally when this occurs it is a issue with the compressor.

You can check the compressor to see if it is ok. Turn the circuit breaker off, Remove the cover on the top side, to access the compressor. Dis-connect the wires from the common, start and run terminals. Using an Ohmmeter at the lowest scale check for continuity between all three terminals. A Lack of continuity between these three terminals indicates faulty windings and the compressor should be replaced.

IF there is continuity between the terminals the next test is requires that you scrape some paint from the side of the compressor and check for continuity between each terminal and the casing. A reading indicates that the windings are shorted to the casing and the compressor must be replaced.

Also if the compressor does not start quickly and easily each time a capacitor may be faulty. When a signal is sent from the thermostat calling for more cooling, the capacitor dumps it's stored power to the motor, providing an extra boost for a few seconds to get it going, this could be the spike you are seeing. The capacitor also should be located on the top side. You may have 2 a run capacitor and a start capacitor, they are round cylinders and you need to be very careful with them. They do store electricity and can give you a severe shock, never touch any two posts on a capacitor at once. I have seen these go bad also, when they do they will melt the wiring on top of the compressor, I would look for any signs of this.

Also with you running the AC on generator you need to watch your load, turning the TV, Microwave or other components my be enough to trip the breaker, I just wanted to mention this, sounds like your problem is with the AC.

Robert
Robert, RV Mechanic
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Customer reply replied 14 years ago
Okay. Well, I went out to the camper this afternoon and turned on the AC. Honestly, I can't tell you whether the compressor was "cycling" or not today, because it was cooling the whole time I was in there. I could only stay for about 10 minutes because I had my 1 year old with me...

I think it cycles, because the last time I slept in there I remember it kicking on and off as needed to keep the temperature down, so I'm pretty sure that it is working.

Anyway, I performed all of the continuity tests you recommended and they were all good - which did not surprise me since the compressor seems to work okay.

There are three capacitors in this AC unit. One is the fan motor start capacitor, easily identifiable by the wires running directly to the motor. The other two, a 20uf and a 50uf capacitor with a resistor attached to its terminals, are wired parallel to one another across a relay box then on to the compressor.

When I perform the simple tests that you can find on the internet, the capacitors seem fine. I also took these capacitors to an AC distributorship recently (your not the first person I asked about this) and they said they were okay.

The only other thing out of the ordinary that I noticed was a dirt-dobbers nest on one of the compressor terminals that could have grounded the terminal out, but I'm not so sure that is the problem, since the compressor will run. It is too late at night now to test the power consumption of the AC.

Would the compressor run at all if the relay was bad, or does that only control the capacitor input to the compressor?

Thanks,

Billy
RV Mechanic: Robert, RV Mechanic replied 14 years ago

OK

Seems like you really have everything covered. One thing I did not mention is the generator. IF you came to the shop we would load bank the generator to make sure it has no issues, this is done at 90% of rated capacity, when doing this it will separate a coach wiring issue or generator issue. I did not mention this because you are on your second generator with the same results. Getting back to the AC unit the thermostat directly should tell the AC to come on. One other check you can do and this may have been done is to check the overload protector.This will open the AC volts to the compressor if it has overheated due to an electrical problem. A weak overload protector will cause the compressor to short cycle or start and stop rapidly. Turn off the breaker for the AC make sure it is at ambient air temp, then measure continuity across the terminals, IF Open the unit must be replaced. This is located on the compressor and may have been checked already. I am going to think about this today and maybe get some other input and get back to you.

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Customer reply replied 14 years ago
Hi there,

I don't think it is the generator - I can run everything else on it, just not the AC (I could never run everything AND the AC at the same time :)

The overload protector read out just fine.

The relay works well, too (though I figured out what it is for - it is used to discharge the run capacitor when the power is shut down).

At this point, I guess I will replace the run capacitor. That is the only thing that makes sense as the issue - the compressor does start and does run, but without adequate help of a good capacitor, it takes a lot of current to do so...

I appreciate your help. If you think of anything else, let me know.

Billy
Customer reply replied 14 years ago
Well, no dice. The new run capacitor did not keep it from overloading the generator.

Any other suggestions?
RV Mechanic: Robert, RV Mechanic replied 14 years ago

OK

I would try this, shut off all the breakers in the camper except the roof AC breaker and run the generator to see if it trips. Also Have you measured the amps off the compressor with an amp clamp?

Thanks, RJ

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Customer reply replied 14 years ago
I haven't yet. I will have to go get one. I am also planning on sitting on top while it runs to check relay operation and to see if the overload is causing it to short cycle.

It runs fine for a while, but something is causing it to kick that breaker after a while.
RV Mechanic: Robert, RV Mechanic replied 14 years ago

OK

Real quick hoping to catch you online, Has this done this since day 1? How is the condition of your house battery? and on the compressor draw you should be able to measure amps off the compressor on the black or blue wire.

Thanks, RJ

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Customer reply replied 14 years ago
Hello,

Sorry I missed you.

No it hasn't done this since day one. We purchased the camper used last September in Mass. We drove it from there to Texas in 4 days, running the AC using the on-board generator while driving and on shore power the rest of the time. We did have to buy a new house battery about 1/2 way home because it had a bad cell and wouldn't crank the generator. It worked well until the last day of the trip when the AC breaker started tripping.

I ran the AC using the generator a couple of nights ago and watched the load meter very carefully. It started out drawing 20% load but gradually climed up to Overload condition over about 10 to 15 minutes of run time. A local AC guy said I should clean the coils and make sure that all of the coil vanes are straight (not crushed) in order to ensure that the compressor can release heat efficiently.

Tonight I disconnected the compressor leads and ran just the fan motor on low, medium and high for a while just to see if the motor could be drawing too much current. No such luck. It didn't even register 10% of the generator's load...

Next step is to buy coil cleaning products, straighten the vanes and see if that works.
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Robert, RV Mechanic
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