Did you check the fuse on the CC Unit? Also this whole system is vacuum, no electronics other than the CC unit and the Check Valve control the system. The CC unit tells the Check Valve which lines to give vacuum too and how much so that it will open the vents as well as control the blend air flap! The blend air flap has a potentiometer on it that will tell the CC what position it is in so the CC can move it to keep the temperature in the car at the desired setting. There are two temp sensors, one in car and one on the top of the fan housing for outside air temp. The CC controls the blend air flap based on input from these two sensors and the potentiometer on the air flap. To get to that potentiometer and flap you can either remove the whole dash or take the glove box out and it is on the left top right below the dash top. It is easier to see and test with the dash removed, plus you can check all vacuum lines and connections this way. There is a full vacuum diagram on the MB Maint CD for the W201 model. Even has what color the lines are. I suggest you pick up the maint CD if you do not already have one, it is very helpfull when troubleshooting this stuff yourself.

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~Jamie
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2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....