1989 Mercedes Benz 300e Lukewarm air

Car had new blower motor installed @ 140,000 miles. Main problem is that the air is only somewhat cool, never gets cold unless its at night, and the air temp is around 70-75. But on hot days, 90 degrees plus, the air is just lukewarm.

I put some refrigerant in the car, and it helped somewhat, but the car is still not cold. I took the car to a mechanic, thinking there might be a leak. He did find a faulty low side cap which was replaced, and also they put die into the car and added 1 lb of refrigerant. Car still cools about the same, not very well on hot days, just makes the inside of the car tolerable. Have tint on all windows but the front, thinking that might help. It has helped, but the car just won't get comfortable.

Any ideas?