air conditioner evaportor coil freezing over.

Old 06-23-12, 05:16 PM
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air conditioner evaportor coil freezing over.

Help! Last yr at end of summer the A/C quit working. The outside unit just quit working. When turn it on it would click but never come on outside. So we decided to tough out summer and get new one this yr. It had previously been freezing over all summer but not everyday. Well summer is here and no $ money for new one . We turned back on and it works but now it runs on auto for 1hr or 2 at the max before freezing over. have to turn just vent on to thaw it out then turn on cool again. this is getting old!!!! Someone told us that just the FReon needed recharging. Please help?
Old 06-24-12, 12:19 AM
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Ok I'm a little confused.. This is all the same unit we're talking about right? Last summer the outdoor unit stopped coming on, this summer it started working again but now the indoor coil is freezing over?

The outdoor unit not coming on or coming on sporadically could be a bad capacitor. Very easy to replace and relatively cheap. If the indoor coil is freezing over then the system definitely does not need refrigerant, because it is obviously getting very cold. It freezes when there is not enough air flowing over the coil to keep it above 32 degrees. When the airflow is low over the coil, the coil gets colder than it should and the air gets 'superdehumidified'.

Think of a glass of iced tea on a humid day. The colder the glass is the more moisture condenses on it and the bigger the puddle on the table. Same thing with the indoor coil. Eventually it gets so cold and it wrings so much moisture out of the air that it begins to freeze. And that is a vicious cycle - the more it freezes the more it blocks the airflow, which makes the coil colder and causes the freezing to get worse - until the coil is completely blocked. How does the airflow feel from the registers when you first turn the system on?

So the first thing you need to look at is your filters. Clogged up filters restrict the airflow and can absolutely lead to a frozen coil. Make sure your returns are not blocked, and if they have filters in them be sure to clean or replace them as well (most systems just have a main filter at the air handler though). If you have recently switched to a high-MERV filter such as Filtrete Ultra Allergen, it may be too restrictive for your particular system. Do not close dampers or registers, as this also reduces the system airflow.

If your system is zoned (you have one air handler/outdoor unit but more than one thermostat), your zoning dampers may be stuck closed or there may be a problem with the zone controller, causing the system to 'recycle' too much air, which can lead to superdehumidification.

Last edited by JerseyMatt; 06-24-12 at 01:14 AM.
Old 06-24-12, 11:16 AM
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Low airflow or refrigerant leak.
Old 06-24-12, 01:49 PM
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You need to have the charge checked by a pro.

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