I have a 1977 240D which I bought new. It has been a great car.

The most trouble I have experienced has been with the vacuum door lock operators.

I have become proficient in replacing and/or repairing them.

My question: Is there a way to determine in which door the faulty operator is located before removing the trim, handle etc?

It would be a lot easier if I could avoid using the elimination method I have used to this point.

Thanks.