I run my A/C compressor off the water pump belt, the alternator is mounted to the A/C compressor and uses a short belt from the unused groove of the a/c compressor. It makes for easy fabrication and theres no need for an extra pulley at the crank. This is on my 250. The alternator runs higher rpm this way, so no problems charging at idle.
Makes plans for a 6 blade solid fan or an electric assist fan, you will not be happy with idle speed cooling without one or the other. I'v had a/c for while now, so every summer I speed up the idle rpm, then when it cools off, I lower it back down. Its the easiest way to keep it happy in slow traffic without over complicate the carburetors. with a step up solenoid.
My 18" flex fan wasn't enough to keep the heat steady at idle, once I switched to a solid steel 6 blade 17" fan, the truck will now stay under 200 at idle in 95* heat, and still blow 40* air. Is all about air flow, the more you can give it, the better the system will work, and it will be much easier on the compressor as the pressure always stays lower. Adding an auxiliary under bed condenser/fan unit would be a good option along with the condenser out front, anything you can do to cool the high side is a plus.
Last edited by Joe H; 07/13/2026 11:44 AM.
