I have a 1979 300SD with a bad climate control servo. Big surprise, I know.

Recently, MB has drastically lowered the price of the basically identical unit for the w123, part # 000-830-03-84. They also lowered the price of the correct w116/107 part, (don't have part# handy), but not nearly as much. There is about a $600 difference between them.

The two units are outwardly identical AFAIK and of course eBay junkyard sellers do not acknowledge that there are even two separate parts, they just advertise the w123 part as being for all models.

Does anyone know for sure what the difference between them is and more importantly, are they interchangeable? The climate systems are outwardly identical in all models of those years, dash unit, etc. We are of course talking about the early w123 system used up until 1980. Thanks in advance as always!