Changes to W126 Climate Control Unit

[Hdavis19]

Hello all!

I've been researching the differences between the early model W126 CCU and the later units. I've noticed that mine (a 1985) is quite different from the later models.

For example, mine has two 12 pin connectors (one for left and right) and the later style ones have two 14 pin connectors. The later ones have built in backlighting, where as mine does not. Wheel location is slightly different between the two as well.

I need more help though. Specifically, can someone provide pinouts for each of these units? What is the technical difference between the 12pin and 14pin connector?

Reason I'm asking is to use a later CCU (14 pin connectors) in an early car (12 pin connectors). I'm replacing the wood trim in my car, and I have wood pieces from a later car with the wheel in a slightly different location. Meaning I have to use the later CCU to fit.

PS: My theory is that the extra two connectors are for the built in backlighting. However, I'd like concrete evidence. All help is appreciated.