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Author Topic: Bad Capacitor on Coleman AC unit  (Read 9216 times)

Howard R

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Bad Capacitor on Coleman AC unit
« on: July 18, 2011, 01:40:00 AM »
My Coleman roof top AC unit has been giving some problems of late.  (Coleman Model 86338766 - Mach3 I think)  .Probably about 2000-01 vintage.

Normal start up is ok but once it reaches the set temp and cycles off, compressor would not come back on, tries and back off .... fan operation ok.

Climbed on top today and checked capacitors, found the start cap is open, other two checked good. (VOM check)  pix attached.  That should be fairly easy to come by for replacement I think.

Attached is the PTCR start device WSX-5CM Motor Starter.  Question is does that need to be replaced also ... how can I check/test that?  From searching it seems that a failure here can cause the cap to fail but in most of the cases I read about there was visible, physical damage to one or both, which I don't have.

So anyone with some experience??

thanks,

Howard
2001 Fleetwood Southwind 35R
V10   F53
Colorado

Bob Buchanan

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Re: Bad Capacitor on Coleman AC unit
« Reply #1 on: July 18, 2011, 03:12:07 AM »
Normal start up is ok but once it reaches the set temp and cycles off, compressor would not come back on, tries and back off .... fan operation ok.

Question is does that need to be replaced also ... how can I check/test that?

My roof top Coleman with ducted air began acting somewhat that way during the heavy heat spell a few weeks back. Sometimes if worked, by then only hummed when I would turn it on. When it did start up OK and run for awhile, the fan would stop but the rest of the unit was still operating so I would quickly turn if off. The fan was working OK by itself for awhile, but then it would not and the hum was all I got.

Took it too AAA RV Appliance in Sacramento. The fan was completely frozen and had to be replaced - plus a capacitor was also shot. They replace the fan motor and the capacitor and did a good cleaning of the fins and so forth - and now it runs better than it ever has in terms of strength of the air and cooling. The fan motor was over $200.00 and the capacitor about $15. With labor it cost me a bit over $400. Was surprised at how big the fan motor was, but with the ducted air, can see why. My rig is a '96, so am pleased that such a unit would last as long as it has.

Why don't you change the capacitor, then see how it runs for awhile?
« Last Edit: July 18, 2011, 03:15:18 AM by Bob Buchanan »
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JayT

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Re: Bad Capacitor on Coleman AC unit
« Reply #2 on: July 18, 2011, 09:07:14 AM »
Quote
Climbed on top today and checked capacitors, found the start cap is open, other two checked good. (VOM check)  pix attached.

A good capacitor will read "open" and a bad capacitor will read as a "short" on your ohm meter. Be careful in reading a capacitor with your meter it can hold a charge for a long time so be sure to discharge it first. By the way you are discharging it both for your meters safety and yours.

Jay T
We have been RV'ing for 20 years and much tent camping prior to our first RV.
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Molaker

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Re: Bad Capacitor on Coleman AC unit
« Reply #3 on: July 18, 2011, 10:03:47 AM »
A good capacitor will read "open" and a bad capacitor will read as a "short" on your ohm meter.
Not necessarily.  If you use an analog meter (and some digital meters), a fully discharged electrolytic capacitor of the size used in start or run capacitors will start out appearing as a short then quickly build up to eventually an open or infinity.  A similar but defective capacitor will either show shorted (or steady low resistance) or will show an open immediately with no gradual build up.  Additionally, a defective capacitor can read like a good one (building up to infinity) and still be bad because it is breaking down under higher voltages than the meter applies.
 
Since few of us have test equipment than can fully test a capacitor, I recommend changing the capacitors if no other obvious cause for malfunction can be found, especially in an older unit.
Tom & Joyce and Ditto the "don't tell her she's a dog" Westie
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rvpuller

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Re: Bad Capacitor on Coleman AC unit
« Reply #4 on: July 18, 2011, 10:28:00 AM »
Change the cap and the start device, normally the cap goes out because of the start device. One way to check a start cap is look at the hole in the cap that has a white filler in it, if it's bulged out and soft it's shot. Also check the terminals where the spade connectors are attached, if there is any sign of arcing they are loose and the cap is shot. Better just replace them both and save a trip to the parts store if you don't have the equipment or expertize to check them out.

Denny 
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JayT

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Re: Bad Capacitor on Coleman AC unit
« Reply #5 on: July 18, 2011, 11:29:47 AM »
Good point Molaker, I was being a little on the simplistic side.  :)


Jay T
We have been RV'ing for 20 years and much tent camping prior to our first RV.
2008 Holiday Rambler Arista 33'
1983 CJ7 Jeep
Amateur radio operator call sign K6RUV
Home is Southern California in the Coachella Valley

Gary RV Roamer

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Re: Bad Capacitor on Coleman AC unit
« Reply #6 on: July 18, 2011, 08:19:52 PM »
The hard start cap and run device are cheap enough - just replace 'em.  I bought them for my Coleman Mach on ebay last winter for under $20. The Cap and run device come as a kit for my model a/c, so clearly Coleman thinks they should be replaced as a set.
Gary
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Howard R

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Re: Bad Capacitor on Coleman AC unit
« Reply #7 on: July 18, 2011, 10:02:08 PM »
I should have clarified I was using an analog meter and did not get the swing on the needle with the "bad" cap, other two were ok.

I'll look for the kit ... kind of what I was leaning towards, but nice to get some feedback from folks that have been there.

thanks,

Howard
2001 Fleetwood Southwind 35R
V10   F53
Colorado