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2006 GMC Sierra A/C blows warm/cold on lowest setting


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Last summer my a/c started to blow warmer air. Everything seemed to be working normally (fans etc.) so I added freon and it worked great until the fall when I stopped using the a/c. Now that its warming up I have tried to us the a/c this spring and more often than not it blows warm air on the coldest setting. Sometimes, it will eventually correct itself and blow cold air but 9 times out of 10 it continues to blow warm air. I try to mess with the settings, off/on, cold/warm, highest/lowest, etc. but nothing seems to help. Any suggestions?

 

Thanks

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When you added it last year didn't you use a hose with a guage on it?

 

If so the guage shows how full it is, you could check it with the guage, when there is some freon in the system you may hear the compressor click on and off over and over becasue of the low freon sensor

 

if you had to add it once then you may have to add it every year (or get it fixed right)

 

Joe

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i hooked up the guage to the system and it gave me a reading of 110 psi which is very high. This was after driving approx 28 miles/45 min. The A/C was running during this time to try and see if it would cool down but never did. Once I was home i put the guage on it to check the pressure. The guage has the following psi ranges: 0-25 (low), 25-45 (filled), 45-65 (Alert), 65-200 (warning). Last year when I filled it, it was filled to roughly 50 psi. Can I drain this myself? Or is this something more in depth and requires specific tools to fix? Thanks for the help.

 

This morning the A/C was blowing cold. The outside temp was 65, the a/c setting was on the coldest setting but the snowflake setting was off and the return setting (picture of a truck with a circle arrow) was on. Sorry I dont know the technical terms for them. thanks again

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110 psi most likely means the compressor was not running at all
(when the compressor is off that is a normal pressure)

 

DO NOT EMPTY IT I am an AC tech

 

I think you will need to have it serviced, Are you saying the "snowflake" won't light up ever?

 

Joe

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Sounds like your compressor is working sometimes and not others, there is a pressure sensor that may have a loose connection or be going bad, there is also an electric clutch that may be bad

 

When the AC is turned on there is a very distinctive "CLICK" at the compressor and then you can hear (and see) it running, don't look at the pulley where the belt is, that always turns, look at the very front of the compressor, have someone turn it on and off CAUTION, watch your fingers

 

Yours may not look like this but # 3 is the low pressure switch, make sure the connector is on all the way

 

2009-11-07_153335_79212376.gif

 

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Great thanks for the info! I know what click you are talking about and will make sure that connector isn't loose. I really appreciate the help! If the connector is bad, can I replace it myself or is it best to have an AC tech do it?

 

Thanks again!

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Not likely sensor is bad just check connection, maybe clutch, are you around a lot of salt over winter

(the AC clutch went on my bosses salt truck)

 

It looked really bad, covered in rust and corrosion, Check them both and get back

 

Good luck

 

Joe

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It's possible to do it all yourself. My suggestion, replace every part of the system! When I did mine, I ended up replacing the drier, compressor, orifice tube, gaskets and o-rings before it all worked again.

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Sorry to disagree

 

It's possible to do it all yourself. My suggestion, replace every part of the system! When I did mine, I ended up replacing the drier, compressor, orifice tube, gaskets and o-rings before it all worked again.

 

Sorry to disagree with you but I would recommend taking it to tech before replacing everything in the system

 

As a Tech myself seldom is it more than one or two things

 

Its all about proper Diagnostics....

 

Joe

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Well, mine was based off of my truck being 10+ years old with 250,000. It was less than $400 for everything, and I did it all myself in 3 hours. That was 2 years ago, and it is still ICE COLD!

 

Truth be told, proper diagnostics would help identify the base problem...

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I checked the connection and it was tight. It worked on my way home for the most part. After 20-25 min it started blowing cool air instead of cold. I had my head under the hood and had someone turn on the AC but never heard the click

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Ok, visually inspect the AC clutch on the compressor, sometimes the coil (electric magnet) that pulls the clutch in has bad windings that work when cool but stop working after they get hot

 

Also, come to think of it, if the truck is low on coolant or slightly overheated the system will turn off the compressor, does it tend to work when the motor is cooler and then stop at some point during driving?

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I'll check the clutch when I'm home.

 

For the second part, I'm not sure. I will pay more attention next time but that could be a possibility. My gauge read 110psi and that's in the "warning" section so I didn't want to add any since I wasn't sure if it needed it or not or if it would screw something up.

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If the compressor isn't turning then you will read a high pressure reading on your gauge. What I did on my truck was to unplug the pressure switch and put a jumper wire in the plug. That way I can see if the compressor came on and then I could get a proper "running" pressure reading. You may want to do something similar just to check the pressures in the system.

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