Heater Wiring Diagram for My 64 C10

[lugeyser]

Do any of you have a link to the proper diagram?

Need help to get the defroster and heater working. Supposedly, my wiring is jacked, along with from what I'm finding everything else the previous owner did themselves.

Thanks and I appreciate it!

[ray_mcavoy]

Welcome!

I don't have a schematic diagram of the heater blower wiring that I can post and the diagram in the factory service manual is more of a pictorial layout of the harness rather than a wiring diagram. But it is a fairly simple circuit.

There should be a brown wire plugged into the side of the fuse panel (connected to the 3rd fuse down from the top) that feeds power to the control switch on the dash. From there, a group of 3 wires (typically yellow, blue, and orange but might vary with some years & heater styles) runs over to a resistor assembly mounted in the air duct under the dash. The orange wire (or black with orange stripe in some cases) continues on through a grommet in the firewall and plugs into the blower motor. The blower motor is case ground to the metal heater box.

With the control switch in the "high" position, it should connect the brown & orange wires together and feed full battery voltage to the blower motor. On the low and medium settings, power is routed through the yellow or blue wire, through one of the resistors, and then on to the motor.

You can do a quick check of the blower motor by unplugging the orange (or black/orange stripe wire) and hooking a fused jumper wire directly between the terminal on the blower motor and the positive battery post. If the motor is good (and has a good ground) it should run at full speed with that jumper wire in place. If that checks out okay, make sure the fuse is okay and making good contact with the fuse holder clips. Finally, use a test light or multimeter to check for power on the various wires at the control switch in each position. Note that a bad resistor assembly will only prevent the blower from operating on the low and/or medium speeds (high speed is direct and bypasses the resistor).

[rvrfoot]

Welcome, Try search for the header wires there should be something.