heater/defrost not working

could b you didnt turn the hot water on. r/s side of truck down by the frame rail near water pump.

 

older truck,

could even have by-passed the heater core--if leaking.

 

Sounds like the fan switch is bad, common issue with older freightliners. As it operates on high (some) and doesnt operate on med or low correct?

 

Actually I think the problem could be the resitr board (can't think of the teck name right now) next to the fan. Fan located in front of passenger seat by feet. Should be 7 torq screw to take off cover. When you take off the cover, take your hand and bang on the motor housing, if the motor starts working, then it's your fan motor. Now for the resistor board, normally located to the left of the fan. looks like a circuit board about 2" by 4". When this board goes, you have nothing but high speed on the fan. So your switch won't work on any other speed but high. If you really feel it's your switch, pull the panel off, take the wires of the switch and test them directly. Switches about 35, boards are about 67 and fans run about 150. Any one of these items r really easy to replace. Just remember how you took the wires off, if need be take one off at a time and put onto your new part.

 

This one is tougher. when you slide the selector to heat, do you hear under the dash the gate open or close? Do yu hear air hissing when you move the selector around? There is more than one door, their located on the blower housing next to the fan. There's an air valve located top left of the housing on the firewall. everything is operated by air. That valve could be toast. Once your aired up, move the selector back and forth, you should hear the doors slaping around. If you don't, Either something fell down inside and is keeping the doors from moving. They r rusted at the hinge, or the actuator valve is toast.. You just have to go from easiest to hardest checking. Good luck.

 

K

 

better get it fixed quick smart before you start heading out towards those cool places like ID, MT, UT