AC cycles frequently

14GMCbz · January 6, 2016

Buying a 2014 Sierra with a V6 engine - a Service Tech. told me that this vehicle has a design flaw that causes the AC to cycle every 15 to 20 seconds in warm weather, at idle which causes idle rpm to fluctuate. I have not had the vehicle in a heated shop to verify. I would appreciate any feedback regarding this possible problem. Tech. said it is very annoying and he would reconsider the purchase. Thanks

Victory14red · January 6, 2016

It's probably not really a problem. My 03 avalanche did the same thing. What may happen is that the compressor cycles on and it increases the head pressure in the condenser coils to the point that the high pressure cycling switch tells it to shut down, and then when the pressure drops it cycles back on.

The reason for this is that airflow over the condenser coils the refridgerant charge which condenses it and lowers the pressure. At idle there is typically no airflow (hence why they put electric fans on condensers these days). Now, the design flaw may be simply that the a/c fan isn't big enough or isn't programmed to run at a high enough speed.

So in other words, yes there may be a flaw. But it's not going to hurt anything as long as the cycling switch works as designed (i.e. cycles off when pressure goes up)