I assume you've checked the static charge of the a/c right?
MAS control the a/c as well as a few other things. Make sure you replace it with the same part number, there is a MB microfiche mistake on the 92 TE MAS relay part number, yours might fall in with that.
I've never opened a MAS to look for desoldering but, it might be worth a shot but, only of you determine thats the problem. Try jumping it out for the compressor clutch.
Project Smoker, '87 603 powered wagon
Hauler, 96 CTD can you say torque?
Toy 73 Cougar xr7 convertible
Acme Automotive Inc.