Hi, 1980 240d 4 speed here.

Just had my a/c system repaired. New compressor, o-rings, Vacuumed out, new oil and refrigerant.

The system works ok (could be better) when I am driving over 40 mph and highway speeds. When I slowdown and enter stop and go traffic, like in todays 90 degree weather, the system blows slightly warm at best.

I notice when the engine temperature increases in stop and go traffic, the a/c stops blowing cold air?
Could it be the condenser fan? I am having a problem figuring this out.
Is there a way to test that front fan?

Thanks.