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Dal Farnworth (Dallas)
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Username: Dallas

Post Number: 474
Registered: 7-2004
Posted From: 75.91.197.59


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Posted on Saturday, March 26, 2011 - 8:20 pm:   

I was given a one year old Coleman Mach III roof wart last year. It runs great for about 2 hours then you can hear the compressor 'load' up and about 15 minutes after that the compressor will shut down, leaving the fan running.
This isn't like the system is just cycling, it's more like the unit itself is dropping the run cap, ( I changed all the capacitors with known good units).
Once, It tripped the breaker, but I traced that back to a faulty breaker that would trip at 11a.

Any ideas?

Also, it doesn't freeze up, it doesn't seem to have anything in the fins of the condensor or the evaporator. I can shine a light through them and see both sides with no restrictions.
George M. Todd (George_todd)
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Username: George_todd

Post Number: 1208
Registered: 8-2006
Posted From: 99.146.10.201

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Posted on Saturday, March 26, 2011 - 9:52 pm:   

Dal,

A compressor won't start with an open capacitor.
A compressor will act like it is overloaded with either a shorted, or oversized capacitor. However, a shorted capacitor will cause the internal overload in the compressoer to trip in a very few minutes.
If the unit was supposed to have a 30 MFD capacitor, and a 35 MFD was installed by mistake, it would probably run ok. But, if a 40 MFD or larger were installed, the comp would overheat and stop fairly soon, because of too much current in the start circuit.

Does the comp restart about 3 or 4 minutes after it stops? If so, its probably a mechanically bad compressor. One other thought is to check and make sure that the condenser fan is tight on the shaft!
If you have access to a clamp on ammeter, read the current draw of the unit at the breaker box, (because its easy to get to there) and tell us what it reads, before and after the load/sound change.
G
FAST FRED (Fast_fred)
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Username: Fast_fred

Post Number: 1485
Registered: 10-2006
Posted From: 66.82.9.58


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Posted on Sunday, March 27, 2011 - 6:25 am:   

Another thought is a drop of water in the freon circuit.

The water freezes plugging the cap tube or expansion valve , after some running , then melts , and the cycle repeats.

This is common if a backyard fix added freon.

FF
thomas flocks (Taflocks)
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Posted on Sunday, March 27, 2011 - 7:34 am:   

stupid question ,but why do you think someone gave it to you?
Dal Farnworth (Dallas)
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Username: Dallas

Post Number: 475
Registered: 7-2004
Posted From: 75.91.197.59


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Posted on Sunday, March 27, 2011 - 9:13 am:   

Thanks George, I'll get my clamp meter out and see what it does.
It'll probably be a few days, since we'll have a bunch of buses coming in for the rally all week long. The capacitors were direct replacements from an A/C guy and I 'believe' they were the same values as the old ones. I will check to make sure.
The unit runs great for about 2 hours, and then when it kicks out, never does start back until it's been shut off for a few more hours.

Thomas, the reason the PO got rid of it was that he had a new basement A/C put into his 5th wheel in an effort to get everything off the roof.
George M. Todd (George_todd)
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Username: George_todd

Post Number: 1209
Registered: 8-2006
Posted From: 99.146.10.201

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Posted on Sunday, March 27, 2011 - 4:18 pm:   

Dal,
Usually when a properly working internal overload trips for the first time during a run, it will reset in about 5 minutes. As it keeps on tripping, the time between resets gets longer.
Please also check the temperature difference between the supply and the return. The difference should be close to 20 degrees. If it is below about 17, the unit is low on Freon, and the compressor motor is overheating.
That still doesn't explain the difference in sound?
G

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