Suggestions to Repair Broken Truck Heater Suggestions to Repair Broken Truck Heater

Q. This morning, I was unable to get any hot air from the heater. The ac clutch was cycling on and off every five seconds. The blend door is working; the controls are set to heat and high fan. I pulled the ac fuse, cracked open the radiator cap; fluid flowed into the catch can. Now I got heat. The overflow tank is constantly going dry, but I have no leaks. Dealer replaced the thermo housing two years ago and the temperature control in dash once looking for an electric problem not related to heating or cooling. It turned out to be a bad fuse connector. I don't have the code scanner with me here at work, so I don't know if there's a trouble code.
A. If you got heat after opening the radiator, you my have air in the system. Since the overflow goes dry, you should have a pressure test done to check system for leaks. It could also be a stuck open thermostat.

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