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Q: AC Blowing Hot Air

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I have a 2005 Mazda 3. The AC is not blowing cold air at all. So initially I figured there was a leak somewhere on the system. I used UV Dye and found out that the condenser was leaking out the freon. I bought a new condenser replaced the old one to find out that the "new" condenser was faulty (leaking out the freon).

Now I returned that condenser and changed it yet again when putting the freon in it is not blowing cold air. Decided to take it into a shop. The mechanic there said that the compressor was bad. So I went ahead and purchased a brand new AC compressor. The mechanic changed it car still not blowing cold air. When looking for leaks there are none that is visible. The mechanic at the shop said the high side is holding the pressure but the low side is not holding the pressure, but it keeps taking in the freon but no visible leaks. He has no clue what is happening.

Any ideas as to why the AC is not blowing cold air with a brand new condenser and compressor ?

My car has 155000 miles.
My car has an automatic transmission.

A: Hi there. The high and low pressure sides o...

Hi there. The high and low pressure sides of the A/C system are connected. The A/C system is a loop. It will not only leak from the low side but retain pressure in the high pressure side.

You make no mention whether the receiver/dryer was replaced either when the condenser(s) were replaced or when the compressor was replaced.

Whenever the A/C system has a leak, not only does the Freon leak out, but normal contamination and moisture in the air gets into the A/C system through that leak. Any time the A/C system has a leak or is opened for any length of time, either because of a leak or because the system was opened to replace parts, the receiver/dryer must be replaced. It's job is to absorb contamination and moisture.

To explain how sensitive to moisture a receiver/dryer (otherwise known as an expansion tank) is, if a new one was laid out in the open on a humid day, within 30 minutes it would have absorbed enough moisture out of the air to render it useless. If that dryer is bad, it will affect the pressure readings between the high and low sides, and effect how cold your air gets. Too low or too high pressure readings can also be caused by a clogged expansion valve. If neither of those components were replaced when the A/C system was opened, start by replacing them both and recharging the system.

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