adamdogg

This is a weird problem. The AC works perfectly usually, but completely stops blowing after about 1 or 1.5 hours of a long car ride. It doesn't stop if it is idling (I let it idle for 4 hours to see if it would happen). Anyway, when it stopes working, the computer will say that the fan is on, but the blower just stops blowing. Nothing comes out. When it works, it sounds fine and blows cold. It isn't the control unit because Mercedes already replaced it. I've had the car at Mercedes several times with no luck.

Does anyone have any ideas? Email me at adam.cohen@earthlink.net. Thanks so much.

herr_kaufmann

That is craziness, a quick way to kill an engine.

Floobydust

If the blower keeps turning, but there is no airflow, it sounds like it might be the evaporator freezing up. This can happen if the compressor control circuit or the the expansion valve is malfunctioning. It can also happen if the evaporator condensate drain tube is clogged - usually at the bottom where it empties onto the pavement. Mud, dirt, or even applied undercoating can "plug" it. Evaporator freeze up usually only occurs after a long drive at speed because the A/C does not develop its full cooling capacity (usually 1 - 2 tons for a car) without the condenser airflow and compressor speed of a moving car. It also takes a while for the condensate to build up and freeze.

Just a suggestion; I've had something similar happen with a different car.

- FD