The temp switch comes on at 52C 125F IIRC. You could test it in warm water / thermometer and an ohmmeter to make sure it is working. Did you feel the dryer if it was getting warm? If you have the manifold gauge set, why not diy? You can rent a vac pump from Autozone. That's what I just did to charge my 85 300D with R152a Dustoff and it is colder than R134a. Time will tell if it is longer lasting than 134a, which does not last in mine and AC performance gets weaker with time (months). This is with the original non barrier hoses.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked