AC Compressor Freezing up

Old 07-09-10, 10:07 AM
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Join Date: Jul 2010
Location: USA
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AC Compressor Freezing up

Okay, so here's my story-

We just moved into an old house that we inherited from my husband's grandmother. Our duct work is under the house and is in bad shape; lots of holes, obstructed airways, etc...but the A/C unit is fairly new and we've had two AC guys tell us that it's in good shape.

About mid-May our AC unit would only blow hot air when we turned on the t-stat. Weirdest thing-we checked all the wiring to make sure it was wired correctly which it was. We finally discovered it was a shorted wire running from the AC unit outside to the thermostat inside. Replaced the wire everything is running fine. While my husband is under the house replacing the wire we find holes in the duct work from critter(s) which he patched. We get rid of the critter(s). Some were really bad requiring a hefty patch that obstructed airflow. About a week later he took the unit apart and cleaned all kinds of dirt and debris out of the unit and off of the coil. A/C is running better than ever.

So, last weekend (first week in July) we ground down a concrete floor in the house. We sealed the room off from the rest of the house and turned the unit off while grinding so as not to get dust into the system. There was some residual dust throughout the rest of the house but nothing terribly significant. It was cleaned top to bottom on Sunday.

Monday the compressor freezes. We let it defrost and check the filter which looks awful so we replace it. It seems to work through the night but the next morning it's frozen. My husband opens up the unit again and and checks the resoirvoir under the intake vent. It's full of debris and mold which he cleans out. Turns it on and it starts freezing again. We threw in the towel and called a tech to check everything. He checks for leaks, freon levels, checks the circuit board, blower motor is fine, etc... can't find any problems. He takes a look at the intake vent and finds one small piece of insulation hanging in front of it. He secures it back to the top and closes up the unit. He takes a look at our duct and says that the obstructions could be the problem. He turns on the unit and it runs fine. He says that we really need to replace the ducts (which we already knew) and that it seems to be running fine but could freeze up again due to the obstructions. He recommends putting a hole in one of the ducts to reduce the friction and possibly stop it from freezing.

We wake up Thursday morning and it's frozen again. My husband replaces one of the ducts and disconnects another (that he's replacing Fri) to help with the friction. We thaw it completely and turn it back on at about 11:30pm. It runs through the night until at least 4am. By 6am when we get up it's frozen again.

He's in the process of replacing the other duct but we're starting to wonder if something else is at work here. Any ideas? I don't think the replacement of the wire in May has anything to do with what's going on but wanted to be thorough.

Please help!
Old 07-09-10, 12:28 PM
Join Date: Feb 2010
Location: usa
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the compressor freezes? could you be more precise? when the unit starts to ice up from lack of airflow across the coil everything freezes, the coil is consumed with ice, and the large copper line to condenser gets covered with ice. but ive never heard of a compressor getting covered in ice atleast not entirely.

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