AC evaporator freezes and no cold air coming through vents - Maintenance and Repair Forum

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AC evaporator freezes and no cold air coming through vents
Sunday, June 20, 2010 8:47 PM

Hello, I noticed that when I have a long ride the AC kinda quits. The air stops coming out of the vents. Yesterday after I came home I popped the hood and notice the evaporator and its pipping where completely frozen. I will take it to the shop but I dont want to go completely clueless so any idea what it might be and how much should it cost? I always try to have an estimate from you guys before I go to the shop so I can be sure they are not taking advantage of my poor skinny wallet lol

Thanks again guys


Anyone driving slower than you is an idiot, and anyone going faster than you is a maniac...

Re: AC evaporator freezes and no cold air coming through vents
Sunday, June 20, 2010 10:06 PM
must be a leak somewhere... just fix it yourself.. you'll save a bunch..
the very minimum they'll charge for you 2-3 hours of labor for that so you're looking at anywhere from 150-250 or more..
if you do it yourself you'll not only save a lot of money but you'll also make sure it is done right and with care
Re: AC evaporator freezes and no cold air coming through vents
Monday, June 21, 2010 1:30 PM
Andrey B wrote:must be a leak somewhere... just fix it yourself.. you'll save a bunch..
the very minimum they'll charge for you 2-3 hours of labor for that so you're looking at anywhere from 150-250 or more..
if you do it yourself you'll not only save a lot of money but you'll also make sure it is done right and with care


If you try to fix a A/C system by yourself without the proper knowledge or tools you will end up causing more problems and will end up with a bigger repair bill when you finally do take it to the a garage. The systems are finicky and proper filling, emptying, diagnostic, and repair procedures have to be followed. There is a reason all of the A/C Techs have to be certified.


BTW, the evaporator is under the dash. The condenser is up in front of the rad.





Re: AC evaporator freezes and no cold air coming through vents
Monday, June 21, 2010 6:24 PM
It is normal for the pipes to ice up after a long run. It doesn't indicate a problem.

If the system works but as time passes by ceases to work and then after being parked for a few hours works yet again but only to repeat the process and slowly work less and less until it doesn't work and this process goes on and on over and over, I'd guess you have a icing problem on the evaporator.
Why? Where do you live? What is the humidity level where you live? High humidity can cause icing as the moist air is sucked over the ice cold coils, the water in the air freezes to the evaporator and slowly builds up thus preventing any air flow.
When you shut off the car, the ice melts and you are good to go with AC until it ices up again.

If there is a bad part, it is probably the expansion valve which has a temperature probe inserted into the evaporator that senses icing and shuts off the compressor periodically to prevent complete icing and complete loss of air flow.

To replace this part will require a lot of work and a complete discharge and recharge of the system. It is illegal to vent the refrigerant into the air so take it to a shop and have it done properly. You can replace the valve if you are handy but then the system MUST be evacuated with a vacuum pump and recharged. Some say the receiver dryer should also be replaced as well when the system in opened.

Dave
Re: AC evaporator freezes and no cold air coming through vents
Tuesday, June 22, 2010 12:02 AM
A/C repairs can be costly because, as previously mentioned, you must be certified to touch the system. PITA if you ask me because we have a discharge/recharge system at our shop and i am fully capable of repairing AC systems, however it is illegial to do so.

anyways, sometimes if your AC system is low on R134a (you guys in the states use the same chemical in your ac systems, right? or are you still using R12?) (free on) it can cause your CONDENSOR to become frigid and have condensation or ice on it, however i've personally never come across such a thing.

since you say the vehicle will completly stop blowing air, makes me wonder if you are having a compressor issue as well. but then again, i'm not certified in AC, so what do i know
Re: AC evaporator freezes and no cold air coming through vents
Tuesday, June 22, 2010 6:57 PM
david keevil wrote:It is normal for the pipes to ice up after a long run. It doesn't indicate a problem.

If there is a bad part, it is probably the expansion valve which has a temperature probe inserted into the evaporator that senses icing and shuts off the compressor periodically to prevent complete icing and complete loss of air flow.

Dave


Is the expansion valve just another name for the orifice tube?



Re: AC evaporator freezes and no cold air coming through vents
Tuesday, June 22, 2010 7:50 PM
Matthew Moses wrote:
david keevil wrote:It is normal for the pipes to ice up after a long run. It doesn't indicate a problem.

If there is a bad part, it is probably the expansion valve which has a temperature probe inserted into the evaporator that senses icing and shuts off the compressor periodically to prevent complete icing and complete loss of air flow.

Dave


Is the expansion valve just another name for the orifice tube?


No, but they do the same job except in different way.





Re: AC evaporator freezes and no cold air coming through vents
Thursday, July 22, 2010 6:01 AM
Actually it doesn't matter if the lines under the hood freeze, you only care about the evaporator freezing. If this freezes then air doesn't pass through it. Frozen lines just means you have humid air and the lines are cold. When your AC runs does water puddle under your car? You may have a plugged evaporator drain.
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