We had a recent incident were the coils in the return air plenum froze.
The filter was not dirty. But due to a problem with our dryer, which
vents next to the exterior condensor unit, there was a lot of lint on
the exterior fan. The repairman said that was the problem, and want to
charge $375 to acid wash it to clean it off.
I know coils can freeze from low freon levels and from low airflow over
the coils due to a dirty filter, etc., but can the inside coils freeze
due to inefficient heat transfer on the OUTSIDE unit?
If you can't get it thoroughly unblocked with a water hose, rent a power
Some even heat the water for you. It is always a good idea to use soft
Never use detergents as many have an oil base the will insulate the fins!
With any pressure nozzle make sure the stream is straight with the fins
or it will bend them!
Air Conditioning\'s Affordable Path to the "Human Comfort Zone Goal"
Do NOT use a pressure washer to clean the coil. You WILL bend
the fins and then you will have a worse problem. Use a
cleaning solution and a fin comb to clean and straighten the
As to the original question, dirty fins outside will not cause
the coil on the inside to freeze up. You are probably low on
You are correct, low freon can cause a PORTION of the indoor coil to
freeze, the portion closest to the expansion valve. Low airflow on
the indoor coil can cause the indoor coil to freeze.
But Low airflow on the outdoor coil will NOT cause the indoor coil to
Probably. I just finished cleaning (DIY) an indoor ceiling mounted
evaporator coil. The service mechanic wanted $500.00 for the job.
I did it with a hose, floor covering, bucket and about 3 cans of
condenser coil cleaner. The finished result looked pretty good.
Didn't even need a fin comb.
But another question... I need to purchase a vacumn pump for
air conditioning repairs,,, probably both home and automotive.
Which size and quality vacumn pumps are used by the pro's ???
Thank you all for the replies; they pretty much confirm my suspicions
that the freezing problem is not due to debris blocking the exterior
fins/coils. Looks like I'll be getting a second opinion from another
Could be a problem in your orifice (debris clog) or TXV (clog or
unresponsive). Not a dirty condensor.
Condenser problems like that are easily diagnosed by playing a garden hose
on it to temporarily improve the heat transfer.
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