Question about 2003 Chevrolet Avalanche

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My a/c keeps blowing hot air

Recently, my air conditioning has been going through phases of blowing hot air when I have the temperature control turned to the lowest setting. Then all of a sudden the cold air will start blowing again sometimes if I turn the a/c off for a while. Also, along with that, the temperature read out on the rear view mirror keeps changing by 20 degrees at a time. My A/C works a little better than Abolts.  Instead of being smart, it seems like mine is A/C's computer is a bit stupid.  I am used to very good ones that when I set it to 72, and it is 74 otuside, they don't do a lot.  The avalanche will still freeze me out.  But if I turn it off, the darn thing actually lets hot air through ( I woudl prefer no air at all, unless a "vent" option had been chosen). Or if it is 69 outside, again I expect very little, but I get over blown with the heat.  Everything seems to work, just with very little modulation.
There are other gremlins in there too, liek I think it is having trouble figureing out where o deliver the air.  Heat shoudl come in low, but it is still coming in through the dash.  I am not sure if it si because the damper to move it low has a problem, or if it is because the comptuer knows that air should be so hot.

Is there some resistor thats getting old and needs to be replaced?  If you think you know, please provide part numbers.
Thanks,  Scott  Mobile, AL

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  • peachsb Dec 01, 2008

    (note that the first 3 sentences of my post should have been a quote of Abolt.  Mine started with "My A/C works a little better than Abolts..." )


    Wow, thanks tepfy.  I believe you could be right.  I was so close to buying a sensor, as they are cheap, but I didn't know how invovled replacing it would be and my gut was saying it was something more.  Mobile Alabama is one of the most humid cities in the country, so I am sure this thing has worked over time on "drying" the air for 5+ years.


    One other thing, though, is when i manually put the air low, it still blows through the dash.  Some may come though the bottom, I am not sure, but certainly plenty is coming through the vents.  I believe I can't be the only one who doesn't enjoy hot air to the face. Would the dryer do that?


    I already have to get the VIN on my radio reporgrammed.  When they put the TECH 2 on it can it diagnose the bad dryer?

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I would check your presure sensore on your A/C lines first, they are cheap and easey to replace, but what it actualy sounds like to me is a bad dryer. which means more money and evacuating the system and replacing the seals. You should not be charged for any freon or R134A as they are calling it now. because they are not replacing that. They are only pulling it out and putting it back in. but the Dryer on the other hand, can be expensive, its that large silver oval shaped object in the back of your vehicles enjine up top. When it goes bad it will do egsactly what yours is doing, then completely stop once it cant go any more. Its caused by a bad seal or usually over years of taking moisture out of the system. so you more than likely have a bad seal some where. good luck. Any other questions you can contact me, if you have the tools I can walk you threw the fix.

tepfy

Posted on Dec 01, 2008

  • James Tepfenhart
    James Tepfenhart Dec 01, 2008

    The dryer has to be diagnosed by a A/C tech. I wouldn't rely on a oil change person who does it on the side thow. there are a lot of litle things that they can miss that there machine won't tell them. The air coming out of the vent sounds like something isn't tight. I don't know if your truck has one of those fresh air filters that you have to relplace under the hood, but I would start there. and see if anything has been melted, or warped from heat. I know when I spent time down in your parts of the country the heat can even melt heat proof molded plastic. It could be just a litle tiny bend in the plastic, something you may not notice without really eyeballing it. check everything that connects to each other by way of molded or snap together fittings for your vents under the hood, because thats the most likely place warm air is coming into the vehicle. The only other is where your heater core is. The only way to stop the heater core from letting heat into the cap is the way the vent was designed. There is a trap door design in your vent system that blocks off your heater core or allows it to flow heat into your air flow system. If the trap door is not closing all the way due to mold or corossion from that humidity, It will stay open just enough to allow a small burst of heat right accross your largest vent that is open. Being your main Vent in the midle of your cab. If you feal daring thats not a job that is to difficult to take on with a Chilton and a good trust worthy friend to help you out. Just mark your screws and even take pictures of where all your screws and bolts went. That way they all end back where they started. Haha. Been there done that if you know what I mean. Any other questions just ask



    tepfy

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