Here's one for the A/C experts. I've converted my '81 300D over to R134. Did a switch of the drier, drew system down to about 30", etc. Everything seemed to function fine for several months. However, now when the engine gets past idle, the cold air from the vents begin turning warm until it seems to blow ambient.
I slow the car down to idle and it begins blowing cold again. I've check to make certain the compressor is running at all times (it does) and the low pressure side (pipe running across top/front of engine) remains cold. Low pressure side is at a rather steady 40 psi.
I changed the climate control module thinking perhaps the problem was there but it has the same conditions. Vacuum is good but I have not checked to make certain all actuators are without leaks but that doesn't seem to be a problem since it shuts off immediately when the key is turned off. Any ideas?