Once again, poster provides no information about the car. Like Model, Year, mileage and maintenance history of Climate Control related components. Also whether the car is R12 or R134a.

I have been through the climate control problems on two different 124's and it really is not so simple. Complicated system. I experienced three compressor failures over 225K miles. My solution was, in both cases, to take it to the MB pros rather than attempt my own amateur hour diagnosis. I needed the car back, and you need all the A/C recycling equipment to do it correctly. Roughly, $1200 to $1500 fix all three times.

PS: I continued to use the original R12 on these two cars, '90 and '92.

Hopefully the solution to your problem will be less expensive.

Steve