Heater Problem A/C Problem

[gsauer]

The problem happens at any level of heat I set it to...when it is very cold and I'm going fast the a/c comes on and the heat is gone...I have to pull over and shut the truck off to get the a/c to turn off. Than I restart and I can turn the heater back on. If the truck is not moving and running...everything seems ok and it dosen't not happen.

[NothinButBowTies]

How about some more information? Year, Model, Trim, Etc?

[99-2door]

Are you sure the AC is coming on, or is it just blowing cold outside air in?

 

Does this happen in defrost mode or just on normal heat?

[budhayes3]

To add to the info that NothinButBowTies asked for...auto climate control?

[gsauer]

I have 1999 Silverado 1500, 5 speed tran., no extras except standard a/c...my coolent level is fine in radiator and jug. I know my a/c is on and cool a/c air is comming out...I can feel it and the a/c light on the botton is on and the 2 lights on the interior and outside air directional bottons are off....and this happens with what ever temp I set it at when the outside air is very cold for heat or defrosting.....remember this happens all by itself.

It seems to me that some internal switch is getting too cold and fails...turning off the heater and/or defroster and turning on the a/c by itself....thanks.

[gsauer]

I have 1999 Silverado 1500, 5 speed tran., no extras except standard a/c...my coolent level is fine in radiator and jug. I know my a/c is on and cool a/c air is comming out...I can feel it and the a/c light on the botton is on and the 2 lights on the interior and outside air directional bottons are off....and this happens with what ever temp I set it at when the outside air is very cold for heat or defrosting.....remember this happens all by itself.

It seems to me that some internal switch is getting too cold and fails...turning off the heater and/or defroster and turning on the a/c by itself....thanks.