w126 1988 300sel

I'm getting a lot of heat thru the vents while driving around with the heater and AC turned off.

The heat coming out the vents only gets worse the longer you drive.

When turning on the AC the heat sort of diminishes but still seems to be affecting the AC performance (blowing cold air).
It's almost like I'm getting both heat and cold air out of the vents at the same time.

The last shop (MB Independent repair shop) I took it to said that it was the Heater Control Valve. He pretty much explained to me that it was a small easy to get to part that is not seating properly. He said it was located next to the battery.

He also said that such valve was not worth buying at the dealer because it was so expensive for such a small part. He continued on to tell me that he would be on the look out for a used valve and explained that all we needed was a valve diagram/seal that was not deformed. He said that when the valves are not used for long periods of time they deform and the seal conforms to a permanent shape that then does not allow it to seat properly when you get it to work again.

Well its been a year and the shop repair owner still has not found a good valve with a good seat, so he says.

This is a back up car and the MB shop owner knows that so i think if it was up to him he will wait another year.

I can't really find any reliable or trustworthy MB shop that knows how to work on HVAC for w126's.

Does anyone know a good shop in southern CA or does anyone here have experience with this symptom?

I replaced the front shocks yesterday and when I finished I went to look for the heater control valve. Looks like an easy fix if thats the real problem.

Any advice is greatly appreciated.