Climatronic control unit from A4B5 in RS2

[Boumbo02]

Hi Everybody,

I am working to restore my HVAC on the RS2 and I am faceing lots of problems .
One most important problem that I have difficulties to fix concerns the Climatronic Control Unit (CCU).
My original CCU is P/N 8A0 820 043 E but it does not operates the servomotors (I have already cleaned the servomotors, the electrical loom is in good condition and the CCU has no visible solder weakness).
I have found an other CCU from A4 B5 P/N 8D0 820 043 H (same design as the RS2 one) and it operates the servomotors correctly when launching the servomotors setup program ().

My question is :

The RS2 CCU is coded « 00040 » as the A4 B5 CCU is coded « 00043 »
I know that the first series of A4 B5 Climatronic worked with the same servomotors as the last 80 B4 (Bosch VMC 7V), that is why I have chosen this CCU to replace my original one.
But the A4 B5 CCU were programmed to work with additionnal sensors: copmpressor speed sensor, ambient light sensor (below the windscreen) and a 5th air temperature sensor (inside the the heaterbox).
My purpose is to setup the appropriate coding in the A4 B5 CCU in order that it works correctly in the RS2 configuration.
Do you have the meaning of these codings for these specific CCUs ?

Thank you for your help.

[varia]

Coding.
ShadowofBob and S2central.net talks about it here
https://www.s2forum.com/forum/techni...to-coupe/page2

Or Ben
http://theprojectpad.com/viewtopic.php?f=11&t=2393&start=325

[johne]

From the work Paul and I did all those years ago the conclusion was that the codes you could change only related to wether your compressor had a speed sensor or not. There's no code changes that let you turn any A4 B5 CCU into an RS2 spec. one.

That said there are plenty of A4 derived CCUs that will work in an RS2. The key differentiator is that only early A4 CCUs had a vacuum driven recirculation flap and you need a CCU that can drive a vacuum driven recirculation flap in a RS2. Later A4 CCUs have an additional motor drive output that is used to drive the recirculation valve.

I have never been able to obtain a list correlating VAG/Hella CCU part numbers with features pertaining to that unit such as coolant temperature sensors, type of recirculated flap drive etc but for some features such as coolant temperature sensor, if the sensor isn't fitted the CCU just uses time calculated from start to assume the engine is warm enough to turn the heater on. Hella must have documentation detailing that information, it would be great if someone could get it.

I have a reasonable selection of CCUs and one day I'll try and produce a more definitive list of which CCU part numbers will work in a RS2/S2 setup but basically any CCU built up to 1996 has a good chance of working. If you get one with an orange display you can take the display apart and change the colour filter out for a red one and vice versa.