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73-87 Chevy _ GMC Trucks => Interior & Equipment => Heating, Ventilation & Air Conditioning (HVAC) => Topic started by: Prong on January 24, 2010, 05:31:50 pm

Title: Testing A/C relay
Post by: Prong on January 24, 2010, 05:31:50 pm

I'm in the process of putting the wiring back into my truck and have hit a snag. My blower motor will not operate via the dash switch. Also, the relay is making a loud buzzing sound when the fan switch is set to high. I've jumped the motor off the battery directly and it works fine that way. Is there a procedure to test the relay that an electrical novice can understand? The truck in question is a 79 with factory A/C. FYI, I replaced the relay and resistor last year, and I replaced the fan switch (in the dash) once this issue cropped up and no change.

Title: Re: Testing A/C relay
Post by: VileZambonie on January 24, 2010, 05:50:05 pm

First clean the connections and plug it back in. If it's buzzing tap on it lightly. To check the relay do you have a test light, a meter and some jumper wires?

Title: Re: Testing A/C relay
Post by: Prong on January 25, 2010, 03:48:51 am

I do have those things. You'll need to explain it like your talking to a 6 year old, because electrical is a big weakness of mine. The truck is at the bodyshop now, but I'll be there on Friday to tinker with it.