Hi, My A/C heater control isn't working well. I can get vent, A/C and defroster but when in A/C or vent it will switch to defroster when under heavy acceleration. I have tested the "can" and such with a small hand vacuum pump and vacuum gauge-these are working okay. I also cannot get any heat, even if I manually open the heater valve on the heater hose. Is it the heater/ A/C control or do I have an air leak in a vacuum line somewhere?