replaced climate unit, new symptoms - got another bad part?

[eric.t]

94 850 Turbo, trying to fix the AC system. Please bear with me, kind of new to maintenance…

Recently replaced blower motor and resistor. ECC control unit failed on me about a month later. Got a used/warranted replacement, and AC is working great but now I’ve got a new problem.

Dampers will arbitrarily switch while driving….things will be normal, then AC/REC will flash and upper vent airflow will switch to lower vents. I never switch any of the fan or position settings to “auto”, and I’ve never had this problem with my old fried climate unit(s) so I’m kind of mystified…

Had some climate codes pre-swap (drivers side temp sensor, driver side damper), but many many more after the new unit…pretty much everywhere, including all 3 of the control selector knobs. Backlight bulbs also don’t light. However, it is powering on and AC is working so there’s a plus.

Basically this thing is either super defective or there’s something else very wrong. Highly rated ebay seller though. Only things I can think:

• Original part that came out was 9144256, new part is 9134820 (which was advertised as 9166550) . Looks identical, same connections, etc. I was told they’re interchangable/compatible for this year/model…anyone know otherwise?

• Any other electrical thing upstream that could cause bad craziness? Is there any kind of reset procedure I’m missing to unscramble the thing after a swap like this? (turned unit off, waited, disconnected battery, waited, swapped, let it sit, reconnected, let it sit, tried it…so shouldn’t have fried it or anything)


TL;DR
Is there any other part or issue that could cause ECC climate control and dampers to lose its mind after a swap when its NOT set to auto mode? Is there an install/reset procedure I’m missing? Trying to figure out if the new control unit is bad or whether my problem is somewhere else entirely.

Thanks for reading, appreciate any advice anyone has.

[sleddriver]

Research my previous threads on my ECC issues. Might find something that will help you there.

[scot850]

There is a calibration process for the servo motors. I think it is in the handbook, if not do a search on here for it. I think the unit you have is defective and would contact the supplier. You can also verify the cross-over part numbers with a dealer parts department.

Neil.