Quote from: "1800guy"What Rrumbler said sounds good to me. More than once I've used my heater as an emergency cooling system helper.
I did that also towing up Sherwin Grade to the Sierras only to discover later that turning on the heater also fired the Air conditioning kinda negating the all the effect of the heat in the cab. next time pulled the wire on the ac. AND later put in a new factory clutch fan that solved years of overheating issues. ED some vehicle do not work this way