AC cycles cold then hot then cold 2000 Silverado

[gbbeil]

After starting in the morning, AC will blow cold for up to an hour. Then, it gradually warms up to what seems to be outside air temperature - California heat. After anywhere from 10 to 30 min. of this and then it will blow cold again for about 10 min., then hot, then cold....

 

When it first begins to get warmer, an immediate sense of increased humidity is felt and the an extremely faintest of odors can be sensed that could be called musty, but again, it is extremely faint.

 

If the truck is turned off for about 10 min. or longer (haven't tried shorter), it will blow cold immediately but begin to warm up after about 10 min. then repeats the cycle.

 

Auto shop first recharged system which only made the cold time last longer at first but cycle continues.

 

Could the blend door actuator be acting up on its own by opening for outside air then closing all on its own? If so, are there more than one blend door actuators on the Silverado?

 

Greg

2000 Silverado

4.8 L V-8

[silveradosid]

sounds like a faulty cold temperature switch. it is inside the heater box and is a tube that is slid into the ac evaporator. if it senses the ac is to cold it will shut off the ac until it warms up and then turn the ac back on

[muddkatt]

sounds like a faulty cold temperature switch. it is inside the heater box and is a tube that is slid into the ac evaporator. if it senses the ac is to cold it will shut off the ac until it warms up and then turn the ac back on

I disagree with this ^^^. My 01 did the same thing and eventually failed al together. It was the clutch beginning to fail. It would eventually kick off, then once it cooled down, would work again. Trying to test it was tough because it was so damn hot under the truck when it was acting up that I could not unplug the connector. I could test it cold and it showed it was good. Once it got really hot under the hood, it would stop.

[gbbeil]

Thanks for the replies.

 

Silveradosid: My AC does get very cold. Operating correctly, does the temperature sensor/switch turn off the AC but allow it to blow warm? Seems like if it was too cold, it would still allow some of that cold to blow into the cabin and stop the compressor for a while. I guess I do not understand how this works.

 

Muddkatt: How were you testing it? Could a code reader tell me what is wrong?

[muddkatt]

Tested the clutch with an ohm meter. Was able to verify 12v down to the compressor. My compressor has a high limit switch that is built into it. I used a paper clip to jump past it while testing.

Once I figured it out, swapped the compressor, orifice tube and dryer. Problem solved and it gets so cold in the truck that you need a jacket on 95 degree days if you set the AC blower on 3 or above.

[muddkatt]

On a standard AC, it does not use a temperature switch. Some SUV's might have had this feature, and maybe a Denali, but standard trucks use a blend door to adjust temperature.

[silveradosid]

yes it will shut down the ac, all ac systems will have some type of cold temperature switch. it prevents the evaporator from freezing moisture in it, which would block off almost alll air flow. also make sure that the engine fan is operating properly. on a 2000 you have a clutch fan, if it is slipping the high pressure switch will shut down the ac system because without proper air flow the system builds up to much pressure

Edited August 1, 2016 by silveradosid

[Beez]

I have the same problem. Were you ever able to figure out what was wrong and fix it? 

[54inches]

Amy updates?

 

I have a 2005 doing the same thing.  90 degree day today in Texas and it keeps us cool for the most part, but it was on High.....

[Black02Silverado]

The more I read into this the more I'm thinking it is the blend doors moving.  Also, if you have a cabin air filter, check it or replace it if you have not done so in a while.