Heater control unit change out.

[eighteenninetytwo]

I am changign my old control unit with AC for a new one without as I dont have an A/C box anymore. whoever rewired the truck kept a 5 pin connector on the control unit and the new one has only three. In short I expect the wire from the fusebox to go to one pin and then to the fan motor directly do I figure out WHICH of the three pins it should go to (on the 5 pins connector it went into a middle pin which doesn't connect now).

[dmjlambert]

What year truck are you working on?
If you post pictures of the connectors on the old and new controller and of the wire connector that would probably help.

[eighteenninetytwo]

Sorry 1975 blazer. Will try to post pics tomorrow. I THINK i might have figured it out on the basis that the switch for on slow and max has variable positions whereas the hot wire from the fuse box is going to be hot and unchanging when ignition is on. I just need to get to NAPA tomorrow to get a new connector.

[eighteenninetytwo]

Ok. managed to finally get a picture: Firstly at the fan motor resistor (pic1) . The way it's arranged is that if the power comes in though a BROWN wire, it goes through both resistors before going to the motor . If power comes in through the BLUE wire it goes through one resisitor before going to the motor and if it comes in through the orange wire it goes direct to the motor with no resistance (presumably that is HIGH setting for the fan). IF that is correct, what I REALLY need to know is where these three wires attach in terms of the three pins on the actual heater control switch junction (pic 2) and which one the power from the fuse box goes to? Of the three pins, two are in line with the movement of the switch and one is offset. The switch has an OFF , low and high setting.