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Air Conditioning Issue


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Any air conditioner techs out there or owners that have had the same problem? The front roof AC has been working fine. Today when I turned it on, the compressor keeps turning on and off and the unit never starts blowing cool air. It has only run on the generator, I don't have a 30 amp outlet to plug into, and it will eventually shut down the generator. The rear unit is working fine. Chuck

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If the blower is not starting it could be a bad fan motor capacitor or a bad fan motor. Take the interior cover off to see if you can see the blower. Does it turn freely.? If not, bad motor. If it does, with the unit off, put the blower in continuous run, give it a spin (in the right direction) and turn on the unit. If it runs, bad fan capacitor.

 

Do you have an amp meter? You can check the compressor amps as well.

 

If the fan or blower does not start, the condenser is not being cooled as well. The compressor will continue to run and finally trip the compressor OFF due to the internal thermal overload. With no condenser cooling, the discharge pressure increases and over heats the compressor motor and trips the overload. If allowed to continue, it can over load the breaker and trip it. If the compressor is bad, it should trip the breaker and not trip the generator. DO NOT let the unit continue to operate. Shut it off and shut off the breaker as well.

 

Ken

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Thanks Ken. The fans run fine. The fan starts and runs well before the compressor kicks in and it runs OK continuously as the compressor comes on and off. The compressor comes on for maybe a minute and then kicks off for a minute or two then kicks on and keeps up that cycle. After a while it will slow down the generator enough to stall it. Chuck

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What you describe sounds like a bad start/compressor Capacitor.

You typically have 2 capacitors, a Run (fan) capacitor and a Start (compressor) Capacitor. Sometimes they are physically separate, sometimes they are within a shared housing with separate terminals. Be careful using your meter on capacitors, they can hold a charge large enough to give you a spiked hairdo, even with the power off.

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To work on the capacitor, kill the power to the unit by shutting off the breaker. Next remove the top cover for the A/C unit. Holding the plastic handle on a screw driver, short the terminals on the capacitor to discharge it. Take the wires of and replace the unit.

 

If the capacitor is the problem, this would be a good time to add a hard start kit to the unit.

http://www.rvcomfort.com/pdf_documents/1976288_copy.pdf

 

Ken

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I'm far from being an air conditioning expert, but I'm thinking that Jim2 may be correct, for several reasons. Start capacitor failure is a fairly common issue with RV air conditioners. When it attempts to start, does it make a humming sound that is louder than the typical sound it makes when running properly? If it is the start capacitor the motor is not actually starting and you could probably verify that by watching it with the shroud off while someone turns it on for you. What happens is that the motor needs added torque of the effect from the start capacitor and if it fails the motor either don't start or may turn very slowly and it also draws excessively high current, which is what is shutting down your generator.

 

With what typical RV service costs and the fact that many an RV tech is not really competent on air conditioning units, it is probably worth replacing that one first, just to see if it will solve the problem. You can probably get one for $30 to $50 with the hard start kit.

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If you know which one you need and have the time, I'd look at Amazon but you may want one more quickly and so can probably get it from most RV supply stores or shops. You will need the make and model of a/c unit to get the right one.

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Replaced all three on our Coleman Mach 8000 Series last year.

As Jim said - You need to check the actual numbers on the caps in the ac unit. Take a picture. You may need to partially disassemble to be able to read the labels on the caps. On our unit all three were strapped together with plumbing hanger strip.

Pictures will also help with remembering the wiring configuration. Take enough pictures to see the whole setup (wiring locations) as well as the label information.

Most of these can be purchased on Amazon and delivered or do a web search with the MFD and VAC settings and you should get multiple locations to purchase.

I bought two on Amazon and one on eBay.

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  • 2 weeks later...

Took the capacitors off the unit today. They are in bad shape and one has disintegrated. There are three. One is a black plastic with Mallory 88-108MFD 235-9847-04 165 VAC and has two "fins" in the top that are all but destroyed. The second is oblong and is a Commonwealth Sprague CSC Pt. No. 325P755H37A23N4XJ 705 MFD +/- 6% 370 VAV 50-60 HZ. The third is the problem. It's round and is so rusted there is no way to read anything off the casing. This is a Coleman Mach unit and a 1999 vintage. Does anyone have the replacement parts to use for these three? I am confused as to what will work. Doing a search gives me too many options and Im not sure which ones I need. Thanks. Chuck

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Advice from another forum led me to the part numbers for the capacitors. Got the parts this morning, replaced all 3. Hooked them up and fired up the AC. Right now, it seems all is well. Keeping my fingers crossed because nothing is usually that simple. Chuck

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