Hi there,
I recently purchased a '79 450SL, and found the heater doesn't work. It has some vacuum leaks, which I'll fix, but the control unit is shot. ($1590). I'm looking at installing the Unwired Tools ACCII upgrade kit, which replaces the old control unit with a digital controller and more standard heater valve, and am soliciting opinions and information from those who have installed the kit. I see they have a revision that elilminates two of the vacuum valves their original kit contains (the original kit had a valve for the recirculate flap, the side/center flap, and the leg flap. The revised kit contains only a vacuum valve for the leg flap.) My question is: Does this eliminate some control function vis-a-vis the original control unit, or are the recirculate flap and side/center flaps still controlled by the original panel controls? I would think it very desireable to retain all the recirculate function when the air conditioner is running.
Thanks in advance for your helpful replies!

Richard Wooldridge
'82 300D/4.3L V6 conversion
'79 450SL - Red (What is the 1979 red called?), Bamboo interior
'75 280C

ive managed to keep the original servo unit working on my 80 300sd.when it works its beautiful.quite a piece of engineering for its day.im committed to keeping the car as original as possible.the original servo can be dismantled and repaired if your ok with small component repairs.if not you can buy a replacement unit with aluminum housing.not sure on the $$ though

I also like reliability. Everything I read says that the ACII system fails about every three years, so I want to get away from that sort of semi-reliable area. Also, the idea of having water valves, electrical contacts, a motor and vacuum switching valves all in one unit doesn't appeal to me. I plan on placing the digital controller behind the glove box but will mount the water valve in the control unit's original position, and mount the three additional vacuum valves next to the coolant expansion tank. This will make for a cleaner area than the car had before the update. I'll let you know how it turns out!

Regards,
Richard
'82 300D/4.3L V6 conversion w/T700R4
'79 450SL
'75 280C
Etc...