I have had ACC problems since buying my 92 9000T. The first ACC had wild variations on the scan parameters that varied from second to second. The flap motors got driven to extremes continually. I junked that ACC. My mechanic gave me one that did cooling well. I bought used ones. They all cool well, but I can't get one that heats reliably. The heat starts OK, but then I must keep turing up the target temp. When I get to HI, I then have to manually turn down the fan and it still too hot. I don't belive the problem is the ACC. None of the ACC unit that I own show any error codes on power up and appear to function normally, except for the lack of heat. If I reset the ACC, sometimes it heat properly for a while, sometime not.
My question is if anyone has a reccomended sensor replacement that might fix this.