A/C Help...

[DeputyPelican]

I'll preface this by stating I've got a 1997 Sierra with a fairly new (replaced approx. 2 years ago) a/c compressor, and I just checked the A/C refrigerant today and it was still within proper range.

For the past three-to-four weeks my A/C has been blowing properly until I reach highway speeds, then it begins to blow lukewarm air. One of the times it began to do this I turned the A/C circulation button off and it seemed to fix the issue temporarily; Now that doesn't even fix the issue. When I first start the truck it blows cold, and it seems to only start having issues after driving for a few minutes. I did replace the A/C module (HVAC control module) a few weeks before the issue began. The module I replaced is a cheap Dorman branded one from amazon. I had to replace the module because the OEM one had the common issue of only blowing at the highest or next-to-highest setting.

What do you guys think... expansion valve or would it be the module? Also, I don't think it's relevant but worth mentioning I'm fairly certain the heater core is beginning to fail due to the gurgling sounds coming from the glovebox area, and the truck unexplainably overheating a few months back after a short road trip.

Thanks for your time.

 

[SUBURBAN5]

What did it do before the dorman?

 

[DeputyPelican]

What did it do before the dorman?

I never had that issue before replacing it with the Dorman part; however, the issue also didn't start until a few weeks after installing the Dorman part.

 

[PlayingWithTBI]

It almost sounds like you compressor's clutch is slipping when it gets hot.

 

[SUBURBAN5]

What brand the ac compressor?

 

[DeputyPelican]

What brand the ac compressor?

Not sure, it was replaced by a mechanic shop and I don't remember being told the brand. Any place on it I could look to find out?

 

[DeputyPelican]

It almost sounds like you compressor's clutch is slipping when it gets hot.

Now that you mention it I do hear the A/C kicking on and off real quick under the hood while it blows warm air. It's only taking around three to five minutes now for the A/C to begin blowing warmish air while idling.

Edit: Forgot to add that the clicks it makes when that happens is abnormal from before. There is no screeching or abnormal sounds other than the usual clicking being faster and different than before.

 

[SUBURBAN5]

Im leaning towards the compressor like PlayingWithTBI. However just curious. Did you do anything to the evap coil and condenser? Meaning clean it or look at it?

 

[DeputyPelican]

Im leaning towards the compressor like PlayingWithTBI. However just curious. Did you do anything to the evap coil and condenser? Meaning clean it or look at it?

I did look at it, and they look fine, but take that with a grain of salt since my mechanical knowledge is fairly limited, lol. I've only been learning mechanical work as I go with this truck and the SEVERAL mechanical issues I've had on the patrol cars I've used in my career.

 

[SUBURBAN5]

Did you put gauges on it? Or just the can that has the gauge on it? Also I think compressor have it on the top or stickers on the side I'll have to look at mine