System Iced Up and Compressor Fan Running with Themostat on "OFF" Position


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Old 08-29-11, 08:07 PM
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System Iced Up and Compressor Fan Running with Themostat on "OFF" Position

I have a system that may be from the 1970's in one of my apartments.

Today, I found that the condenser/compressor fan was running full time even with the digital thermostat switch on "off." Then when I'd turn on the fan to "on," I'd get no air out of the ceiling vents and no suction at the only return!

So then I went into the attic and saw a huge hub of ice, the size of a fist, on the insulated tube going into the air handler. THEN when I went down to the compressor/condenser, there was another fist-sized hub of ice on the tube going into the compressor/condenser.

I am guessing that I go no air flow because it is likely that there's ice clogging up the air flow??

So ...WHAT would cause the system to suddenly ice up and make the compressor/condenser fan run full time EVEN when the thermostat is set to "off?"

Thanks in advance! -tony17112acst

P.S. I will be returning in the morning and can maybe bring back more info.
 
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Old 08-30-11, 04:03 AM
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most likely the contactor has welded closed........
 
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Old 08-30-11, 04:55 AM
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I'm not sure what that means. I haven't had a contractor work on the system; it's been running for the 5 years that I've owned this building. Any other thoughts?

Update: I am now here at the apartment and as I guessed, I have cool air AND free airflow (which was not the case yesterday). It seems that the ice totally blocked air flow and now overnight melting gives me airflow now. Secondly, when I turned on the breakers to the system, the compressor/cond fan kicked on without the thermostat telling it to. I'm guessing the compressor is on fulltime since that would explain the icing up.

So the big question is: what would cause the comp/cond fan and compressor itself to run full time when the thermostat is set to "off?"

Thanks!!
 

Last edited by tony17112acst; 08-30-11 at 07:25 AM.
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Old 08-30-11, 08:47 AM
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The contactor (not the contractor) in the outdoor unit is stuck closed. Check and verify it is closed even with all the power off... google air conditioner contactor to visually view what they look like... im on my mobile or I would post a picture.
 
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Old 08-30-11, 10:51 AM
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Oh, that's my dyslexia at work again! It's getting bad, sorry to say.

WOW, you're awesome ...helping me while on the go; thank you! OK, I'll check it out. I'll probably post soon what I found. Thanks again! -tony
 

Last edited by tony17112acst; 08-30-11 at 11:41 AM.
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Old 08-30-11, 11:39 AM
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OK, I just got back from the attic. The condenser is up there in a cavity in the gable end of the building.

Anywho, BINGO! I found that the contactor was stuck. Being careful of capacitor discharge, I nudged the cantactor and it instantly released. I pushed it in 50-60 more times and it never stuck once. I came back down and the fan is no longer running full time! ...only when calling for cool.

I will get some contactor cleaner and spray it and if this happens again, I'll just replace it. I now know how this works and what the contactor does and can do after googling it as you suggested.

THANK YOU, THANK YOU, THANK YOU !! (in a Gomer Pyle voice) This saves me $200 at least! AND the new tenant is moving in in two days, so I don't have a major problem for her as she moves in.
 
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Old 08-30-11, 11:52 AM
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New contactor is probably less than $20....why wait? If it stuck...you probably had arcing or wear of some sort which means cleaner won't really help. Would you rather spend $20 now...or get a call on the 4th of July that the a/c isn't working?
 
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Old 08-31-11, 04:46 AM
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If more sticking is sure to come in the future, yes, I'll change it out assuming it's available. This system is from the 1970's and is still kicking somehow.

I'm now having trouble with it cooling the place ...it doesn't get below 77 in the 520 sqr. ft. apartment. It's in the attic and it's like 110 up there, even with the power roof vent. he ducts are covered with R13 insulation. The air coming out feel real cool ...I'll take a temp measurement of the air today.

Thanks again!
 
 

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