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Old 06-20-2019, 01:49 PM
Grrr!'s Avatar
Grrr! is offline
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Join Date: Aug 2001
Posts: 16,338

What the heck is going on with my AC?

Last night I had the thermostat set at 74. It seemed to be struggling, as it brought the room temp down to 76, but then it just stalled. The AC stayed on non stop for several hours and never went below 76.

I remember thinking: "As soon as the sun comes out, this AC is going to go out on me".

Well, it never went out, and ironically, when the sun came out, it managed to get my home down to 74.

So it couldn't do the job when the sun was down, but now that the sun is up; it works??

What gives??

FTR: I didn't have the oven on last night.
Old 06-20-2019, 02:03 PM
Joey P is offline
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Join Date: Jun 1999
Location: Milwaukee, WI
Posts: 28,970
Start by making sure everything is clean.
Check the filter. Go outside and check the compressor. Make sure warm air is blowing out the top and hose any leaves and garbage from the outside of it.
While you're there, the fan should be running and the compressor should be running.

Go inside to your indoor unit (part of the furnace). Make sure the condenser is clear of both dirt and ice. If there's a panel in the plenum (the sheet metal above the furnace) that's attached with screws, you can remove it and take a look. If it's dirty, clean it. If it's full of ice, turn the t-stat to off and the fan switch to on and let it blow for a few hours.

That's about all I can guess without some more info...
Is the inside motor going?
Is the fan on the outside unit going?
Is the compressor (outside) running (it's separate from the fan, you should be able to hear it)?
If the compressor is running, does it remain running or cycle on and off before the t-stat is satisfied?
Can you feel air blowing from the vents?

I don't think the sun has anything to do with it, unless you notice a pattern, it sounds like a coincidence.

I know, lots of questions, but I'm trying to get a handle on the symptoms.
Hopefully, it's just a dirty filter or clogged compressor coil. Worse case scenario, you lost your refrigerant.
Even a minor electrical issue is easy to fix if your handy.
Old 06-20-2019, 02:59 PM
QuickSilver is offline
Join Date: Mar 2000
Posts: 18,573
What are the common causes for the freezing over of the coils if the filter and outdoor unit are running and clean of debris?
St. QuickSilver: Patron Saint of Thermometers.
Old 06-20-2019, 03:02 PM
Inner Stickler's Avatar
Inner Stickler is offline
Join Date: Jul 2005
Location: Minnesota
Posts: 15,060
Low refrigerant.
Old 06-20-2019, 03:14 PM
KneadToKnow is offline
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Location: Charlotte, NC, USA
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We had this problem (coils icing) when we were using too high a quality of filter. It just didn't allow the airflow over the coils that they were designed for.

At least that's what they told us. We switched to crappier filters and the problem has gone away.
Old 06-20-2019, 05:11 PM
Joey P is offline
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Join Date: Jun 1999
Location: Milwaukee, WI
Posts: 28,970
Originally Posted by QuickSilver View Post
What are the common causes for the freezing over of the coils if the filter and outdoor unit are running and clean of debris?
Low refrigerant will cause them to ice over, but not typically the entire thing. It's usually just a section of it.
If the filter is clean, the next thing I'd check is that the evaporator coils (the inside ones) are clear. If they're full of dust or mildew or anything that'll restrict airflow, you'll have problems.

If you (or the OP) can't access the evaporator coils, let the unit run in Fan On (just the fan, not the ac) for a few hours and see if that helps.
Old 06-21-2019, 12:58 AM
Snnipe 70E is offline
Join Date: Oct 2008
Location: San Jose, CA
Posts: 4,029
Check air flow. Is air coming out of the registers. And what temperature is the air coming from the registers.
Old Snipes do not die they just loose their steam


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