AC question

Tiny
GARDEN111
  • MEMBER
  • 2004 HYUNDAI SONATA
  • 6 CYL
  • 172,000 MILES
My air conditioning stopped blowing cold air. We added Freon and it blew cold air. As time went on it lasted less and less until now it does not help at all. I brought the car to a mechanic and he stated I needed a new compressor and quoted me $800.00 for part and labor. I watched your video and based on it there could be several different reasons as to why it does not blow cold air. It seems most of the problems are with other parts and does not really mention replacing a compressor. Question is, how likely is it that you would have to replace a compressor if the system is still blowing air but it is hot? I am just concerned that it could be one of the issues you mentioned which would definitely turn out to be a less costly repair. We are kind of friends with this guy but not sure I believe replacing the compressor is the problem. What are your thoughts and suggestions? Thanks
Saturday, August 19th, 2017 AT 2:52 PM

3 Replies

Tiny
CARADIODOC
  • MECHANIC
  • 34,163 POSTS
Blowing air and making it cold are two totally different things. The fan blows the air in. The heater/ventilating/air conditioning system, (HVAC), is responsible for making that air hot or cold. You will find the air still can get hot when you turn the heater on. The compressor is just one part of many in the AC system that makes the air cold.

My concern is if you added refrigerant in the past, how did you know when the system was full? The AC system works on the principle of a liquid becoming very cold where it turns to a vapor. If there is too much refrigerant in the system, or too little, the liquid will be turning to a vapor under the hood, not inside the dash where it is supposed to do that. Also, over-charging the system can be a lot more harmful than an under-charge. If there is too much liquid, it can slosh out and get into the compressor and damage it. Compressors can only pump a vapor, never a liquid.

If you over-charged the system, the air coming into the car will not be very cold. Or, if the system is under-charged due to a leak, you will also get warm air. That leak must be located and repaired to prevent the repeated loss of refrigerant. Unfortunately, there is no easy way to know how much refrigerant is in the system other than to recover what is in there, then pump in the exact measured amount. Only older Chrysler products had a sight glass to let you see when the system was properly-charged.

As for the compressor diagnosis, that is not the most common cause of the system to stop working, but I have no reason to second-guess the mechanic. If an internal valve is broken, it will stop pumping the refrigerant, and you will have warm air. They also have a seal at the front. If that starts to leak, the loss of refrigerant will also result in warm air.
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Sunday, August 20th, 2017 AT 4:41 PM
Tiny
GARDEN111
  • MEMBER
  • 2 POSTS
We brought it to Advanced Auto and they put refrigerant in it. At first it worked, air was cold. It lasted a year then went back to warm air. Went back to Advanced Auto and they said there was none and again added some. This time it only lasted for about two months they checked it and it was empty, but this time they used the one that has the stop leak stuff. They filled it again and it lasted three days and then we were back to warm air. That is when we brought it to a mechanic and he told us we needed to replace the compressor. I do not know this is kind of why I questioned the suggestion of replacing the compressor.
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Monday, August 21st, 2017 AT 8:26 AM
Tiny
KHLOW2008
  • MECHANIC
  • 41,814 POSTS
There is a leak in the system and if the leak is detected to be from the compressor, then it has to be replaced to resolve the problem. Was any leak test performed and has the compressor been confirmed to be culprit? Leaks can occur anywhere in the system and usually it is from the evaporator, seldom from the compressor though it does happens.
Is the mechanic an air conditioner specialist? If not, get a second opinion.
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Tuesday, August 22nd, 2017 AT 6:47 AM

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