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Old 04-19-2009, 01:09 PM   #1
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Location: Pennsylvania
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SUN #19
AC compressor kicks off sometimes ???

Yesterday I ran the AC for first time since last season.

I have noticed this before as well, that on the "Low" speed fan setting that that AC Compressor seams to kick off sometimes. When it does the fan of course continues to run and then after several minutes the Compressor will kick back on run 10 minutes or so then maybe kick off again. Cycling on an off a few times untill the thermostat is satisfied.

I have never noticed the Compessor kick off when the Fan is on the "High" speed setting. It always runs continiously untill the thermostat is satisfied.

Is this normal ??

I know the Compressor is suppose to kick off if there is iceing on the coils, maybe that what is happening.

On the low speed (Fan) setting the coils start to ice up, maybe quicker than on the "High" speed setting. I'm guessing maybe on high there is more cool air being extracted from the coils there for no iceing and no kicking off the compressor. I'm really guessing on this, maybe someone can shed some light on this subject.

P.S. I usually set the thermostat at 70 ish, some times 68.

Any info appreciated.



2002 Sunline model T-2975 (large Bath)
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Old 05-28-2009, 09:42 AM   #2
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This can happen because the "head pressure is at the maximum" What this means is that on low speed the refrigerant can't boil off as quickly and the pressure on the compress side has reached a preset limit. Some unit will cycle and it is not a problem. If its cooling OK don't worry about it.

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Old 05-28-2009, 10:07 AM   #3
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One other thing to keep an eye on is the thermostat itself. If you still have the original Duotherm, they tend to lose accuracy over time. That can well affect how your AC behaves.

The best fix for a malfunctioning thermostat is to do the digital conversion. It is easy, and much less expensive that simply replacing the Duotherm. Full info about that is at:

Search here in the Modifications section on key words: digital thermostat for helpful hints about doing the upgrade. A number of us have done it and I can tell you from personal experience that I would do that mod on a brand new RV the day I brought it home.

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Old 05-28-2009, 10:26 AM   #4
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Bob & Steve

Thanks for your info.


It's working okay so maybe I'll just leave well enough alone.


I'll keep the digital conversion in mind, for the future.

Thanks again

2002 Sunline model T-2975 (large Bath)
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