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Heater / AC Controller


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I don't know if I am looking for help or a place to unload. I have been through my HVAC system in my 1990 C4 every which way I can. I checked for Flap operation and none of the motors respond to the controller. I jumped power to 4 of the 5 motors and they move when powered directly. I bought the Durametric package but at this age all I get are codes saying that the flap motor is not working. because this controller seemed to be a problem I went ahead and sent it to Auto ECU in Tennesee. They charged me $500 CAN and returned it. All I found was that there was asticker on the bottom saying it tested OK. I plugged the unit back in to the car and the only improvement was that the little fan on the back turned for about 15 minutes then quit. Everything else worked the same as when I sent it to them. I went through and checked the unit further and found that there is no signal voltage nor power to the Flap motors. I have all the same faults showing as before (after clearing them several times). I contacted Auto ECU and asked them about a service report or some information as to what they found. I got an e-mail back saying I should send it in for warranty. I did this (at cost of $100 CAN) and again received it back with another sticker on it saying tested OK. I plugged it in and this time nothing works. At least before I could turn the AC Condensor fan off and on as well as turn the rear booster fan on by pushing the Defrost button. Now nothing works. I contacted them and they suggested that maybe the main power contact inside came off during shipping, go ahead and return it for warranty. They still have never said what was wrong or what was repaired. Anyway they also put stickers over the screws so that warranty is void if I open it. At $100 every time I am undecided about returning it.

Does anybody have any suggestions. I may go ahead and open the unit to see if there is something obvious. I would like to buy a unit but I don't really want to spend the $2000 that I have seen for a new unit. The other problem is that to modify to a 993 unit you need to jump a wire. The opening that the new wire goes to already has a wire in mine. My other option is to make my own control panel using manual switches to move the flaps and power the other functions through the original switches.

If someone has any advice I would like to hear about it. I don't know anyone with a functional unit so trying another one isn't possible. Anybody know of another repair company.

Thanks for letting me tell my story, hopefully it may help other people in deciding who to send electronics to.


Bob Lendrum

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  • 2 years later...
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I had the same problem with my unit. I bought one for parts from EBAY for 75.00 and simply replaced what was the defective switch, has been perfect for a year. I kept the old unit in case I needed more parts in the future. I saved over 1800.00 in parts and learned a bit by opening up the unit. Fairly straightforward design and easily swappable components. Turns out that even if I had known it was only the switch, it would still have cost me 210.00 for a new one. Good luck.

1991 C2 coupe

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