78 C10 A/C question
 

How do I tell if the fan switch is working without taking the dash apart?
My A/C wont fire up, fuse is good and power to the red, hot side of the fan reley. I jumpered across the low pressure switch at the accumelator still wont fire . when I jumper across the reley red to the yellow everything starts and cools but the reley gets very hot! What next?

Re: 78 C10 A/C question
 

Try completely bypassing the high blower relay and see if you can get a constant speed out of the blower motor. From under the hood you should be able to hear if the motor kicks on high or not. If it does, you have a bad relay or bad connections, which is what it sounds like to me. If it doesnt, you have a wiring issue and need a diagram.