AC Diagnosis?

[moover]

Another AC question here during the summer! I've got a 2005 Tahoe LT 5.3L and the AC blows ice cold until it gets around 90deg outside or 85 and humid - then it will blow cold for 10 minutes and then switch to a sort of warm muggy blow. If I stop and turn the car off/on, it'll reset and blow cold again. Sometimes on the highway it will get warm, then 15 minutes later it will switch back to ice cold and maybe even stay that way for another 2 hours. Basically, it varies when it may come and go, but always is hot outside when there are issues.

Last year I replaced the evap core - air was even colder for a bit, but the same issue stayed around. Is it a compressor or maybe a simple valve issue?

Let me know what yall think and thanks in advance.

 

[Doubeleive]

the 2 dial digital controller is known to do this, but could still be something else

 

[Matthew Jeschke]

That's odd. What year is your truck? Mine has a mechanical fan off the water pump. It will do that if I stop at a light and idle for a while.

 

[moover]

the 2 dial digital controller is known to do this, but could still be something else

Thanks. Where's this located? Something an amateur could replace himself?

 

[moover]

That's odd. What year is your truck? Mine has a mechanical fan off the water pump. It will do that if I stop at a light and idle for a while.

2005. Temp does okay in idle - its pretty random when it chooses to change temp

 

[swathdiver]

Another AC question here during the summer! I've got a 2005 Tahoe LT 5.3L and the AC blows ice cold until it gets around 90deg outside or 85 and humid - then it will blow cold for 10 minutes and then switch to a sort of warm muggy blow. If I stop and turn the car off/on, it'll reset and blow cold again. Sometimes on the highway it will get warm, then 15 minutes later it will switch back to ice cold and maybe even stay that way for another 2 hours. Basically, it varies when it may come and go, but always is hot outside when there are issues.

Last year I replaced the evap core - air was even colder for a bit, but the same issue stayed around. Is it a compressor or maybe a simple valve issue?

Let me know what yall think and thanks in advance.

That's almost always a sign of low refrigerant. Put gauges on it and check that first.

 

[Doubeleive]

Thanks. Where's this located? Something an amateur could replace himself?

well either you have the digital control with LED's or you have a slider manual control with knobs that "click" to the various settings
as shown below

 

[Doubeleive]

as james noted best to check it with a gauge first
that digital control w/auto function is the one that "CAN" go goofy and do exactly like you are reporting
there is no fix you basically have to replace it and they are not cheap, so best to rule everything else out first.

 

[moover]

Got it, sorry - yeah I've got the sliders. Let's hope its not that

 

[Scottydoggs]

my driver side blend door actuator was doing the exact same thing. put a new one in and im back to full control. driver side at any given time would turn full hot. shut the truck off and restart back to ice cold. in the winter it would come off heat and blow cold air too. id also hear it clicking sometimes.

 

[Doubeleive]

my driver side blend door actuator was doing the exact same thing. put a new one in and im back to full control. driver side at any given time would turn full hot. shut the truck off and restart back to ice cold. in the winter it would come off heat and blow cold air too. id also hear it clicking sometimes.

yep, could the be the actuator as well

 

[Matthew Jeschke]

My friend's truck has the sliders too. It's also a 2005. Does the same thing. Have you tried fiddling with the temp setting on the slider? He wiggles his up and down and it goes back to blowing cold for a while.

Also, is it doing it to both sides, or one side? If one side, which side? My friend's does it to the passenger side.

my driver side blend door actuator was doing the exact same thing. put a new one in and im back to full control. driver side at any given time would turn full hot. shut the truck off and restart back to ice cold. in the winter it would come off heat and blow cold air too. id also hear it clicking sometimes.

The newer trucks I think have a reset / learn function for the blend doors. Mine is still the old style w/o that. I took some of the actuators apart and fiddled with them... Actually got one working again. The issue is when they age there's a limit switch in the actuator. If it turns too far it will shut off the power connection to the little motor in the actuator. I had to reset that but eventually the whole thing went bad. I was the "limit switch" in the actuator.

 

[Tazman100]

Replace the blend door actuator

 

[latvius]

My 2005 Tahoe had something similar BUT my recirc door never worked and I never fixed it I could get by without it. Here recently I had symptoms like you mention when it gets really hot outside. Has freon, pressures all good, rear blew colder than front. Changed out the recirc door actuator (I didn't think this would fix it).
So now when I drive around and start to wonder why my a/c isn't blowing cold I realize I didnt push the recirc button, now it is so cold I have to turn it down when it is 90+ outside.
So short story is - does your recirc door work, as in you can hear the difference in the air flow when you turn it on?