I have a bad blend door actuator on my father's truck (2002 3500 stock) ordered a replacement and all I can find is 4 pin units when plugged it it only rotates 1 way and makes a full 360 turn ( when installed it goes hard agains the blend door in the cool position. no matter the temperature setting. The old unit was a 3 pin but every part numbers listed is for a 4 pin. Am I missing something?

Are you referring to the wiring connector to the blend door actuator that shows a three-wire connection? It looks like others have had the problem you are having.

Have you confirmed that you really have a blend door motor actuator problem, or is it possible that the interposer (plastic shaft) is cracked and slipping on the old one? In that case, you can just replace with Heater Treater's steel interposer. You will have to reset the gears though. Heater Treater has a video how to get the gears timed.

• John

Correct the 3 pin vs 4 pin "male side" with the pins on the green board. The wiring harness or "female side" has a blank block that will fit up to 6 wires ( only uses 3) and it is 100% the actuator replaced the adapter and even went as far as to swap the 3 pin bad motor with the working motor from the 4 pin however the green board itself is actually bad ( sat full of coolant from bad heater core)

Is your part number 604018 (a Dorman part number)?

From what I have read on-line, this blend door actuator motor is universal and should work on your truck. It seems that there should be a calibration procedure, but I cannot find one on-line. It might be worth a call to the manufacturer to see what they have to say.

Another possibility is to find a used actuator motor from a salvage yard.

• John

I have a off brand version from amazon that should replace the doorman part number ( could be the problem) I'll call doorman up and see about the calibration procedure