When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Can someone shed some light on how to wire a relay so it triggers when the a/c is turned on. I've checked both sides of the plug, both provide ground when the a/c is on or off. I have a feeling I'm missing something simple (I'm sure the beer isn't helping.)
There are several ways to "tap" into the A/C on/off cycle, but one sure way is to tap into the line that triggers the e-clutch for the compressor and use that voltage to enable a relay. Using this line, there should be adequate current there to just tap into it and take the new wire to your single fan control relay (this will go to pin 85 or 86, whichever one you currently have the +12 going to now). If you think you need another relay, use that new wire to activate it and wire it up to activate your fan control relay - this way, if your thermal switch isn't ON when the A/C comes on, the voltage from the A/C tapped line (or new relay) will activate the fan control relay.
If you use an additional relay between the A/C and the fan control relay, it doesn't need to be "heavy duty", it's not going to be carrying much current, only enough to activate the fan relay (probably not much more than an amp, depending on the relay).
I had installed a few 200amp relays and they were holding up fine when I sold the truck last October. It might be work looking into the dual fan setup from a 2010+ Silverado (I bought a 2012) and see if that can be fitted onto the radiator.
