Heat/Air Conditioning Control Problem

[schaack2]

A couple of days ago, the heater/air conditioning control unit in my pickup started acting up. My pickup is a 1992 K2500 w/ 6.5TD.
When I try to turn the unit on, all of the arrows (5 I believe) on the vent selection begin flashing. They continue to flash for a couple of minutes and then stop. If you try to select a position again, it starts the flashing sequence over. Doesn't matter if I try to select defrost, floor, or vent. The fan speed buttons still work as does the temperature adjustment from cold to hot. From searching past postings, I thought I read that the air diverters in the ductwork are controlled by stepper motors. Is it possible that I have a bad motor. My guess is that the head unit is malfunctioning rather than a motor. If this has been covered in a past thread, could someone let me know what to search for. Any help would be greatly appreciated!

[BobND]

Unplug the "head unit" from the dash, and clean the flat terminals. The can be polished with a pencil eraser. Finish with some terminal cleaner.

If it doesn't work when plugged back in, replace it.

(The damper motors are a DC servo, with NO feedback. The get a command from the head unit to move to a certain position, unfortunately, there is no feedback, so the head unit doesn't know if they obeyed the command to move to a certain position, or not.)

[JohnC]

If you need one, I've got one you can have cheap!

http://members.aol.com/gmc65td/heatcont.jpg

[ 02-22-2006, 01:18 PM: Message edited by: JohnC ]

[woodchuck]

If he doesn't need it my '92 GMC could use it. I imagine the Silverado and the Sierra use the same unit.