2008 3.0. A/C does not always come on until I switch the control to another setting. EG on regular a/c. blows hot. Switch to Max, a/c gets cold. And, visa-versa. Appears to be more prevalent at idle. Changed a/c control switch, no improvement. One shade tree mechanic told me I might need to re-flash the ECM. The dealership said they never heard of that fixing the A/C. Anyone have any ideas? Thanks.

 

Please explain better. Are you saying if you start the car with the AC switch on normal AC, it won't run the compressor, but then if you swap it over to another setting and then back it works? Does it work in every position on the climate control panel?

 

Thank you for your reply.
If I start the engine with the A/C in either regular A/C or Max, half the time it blows hot air. The compressor appears to go on and off. If while the engine is running, I switch the control to either of the other A/C setting, the air blows cold. if I switch it back to the original setting, it sometimes blows hot and sometimes stays cold. The other control settings appear to control the doors as they are supposed to. If when it is blowing hot, I select defrost or up/down vent, it starts blowing cold. I then can switch back to the original setting and again it will either blow hot or cold. As noted before, I changed out the control switch (Motocraft) with no better results. I also checked the freon which is within range. The A/C works well in any of the appropriate settings while I'm going down the road at a steady speed. This mostly happens at idle or in town and especially when I start up.

 

Does this happen in any other climate modes? Sounds like some electrical connectors and grounds need to be cleaned

 

heater and fresh air control selection works fine. Are you thinking connections in the engine compartment?