One important item with A/C systems is the total charge. OVERCHARGING is very harmful. The 190E uses a max of 2.2 lbs of R12 & only about 1.8 lbs. of R134a.
The expansion valve is underhood near to the brake booster. Just remove the plastic air grill & follow the 2 A/C lines to it. Takes about 1 hr with the system discharged.
One thing about the old GM compressors, the belt has to be tight!
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)