[mrein3]

I converted my truck from non-AC to AC.
They factory relay was on the behind the glove box stuff box I bought but I still rigged up my own. Here is what I did.

I took the wire from the fan switch that is hot when you want high-speed. I made this a control wire to a bosch style relay. Right from the positive junction block on the RF fender I ran a 10 or 12 gauge wire to the relay. I put a 20 amp fuse in this wire, under the hood, on top of the RF inner fender for easy access. Then from the hot when energized prong on the relay I ran 10 or 12 gauge wire to the fan.

I use the same relay for hi beams, low beams, hi-speed fan, and driving lights. I keep a spare in the glove box. I had one fail a while ago but that was because my truck was parked outside that winter and water was dripping on the relay around the hood. I moved the relay to a dry location and no longer have a problem. (That was a headlight relay. The fan relay is screwed on to the heater ducts).