Need more help with my '93 500 SEL's AC system. Here is the problem:

1) works fine for about 10 minutes
2) heat comes out of the two driver AC vents. Cool air is coming out of the passenger and rear vents.
3) push the cool air button on the center dash and cool air comes out of the center vents. (Leftmost is still hot)
4) No code failure in the Climate control's diagnostic computer (my mechanic checked this also)

Sometimes the air from the driver's vents pulsates from blazing hot to almost cool. This one has stumped me and my mechanic.

Any suggestions?

Thanks,

John