My car is a bit different...

First my fan would not work. I had rebuilt it so I knew the brushes, etc was fine. I jury rigged a switch from the lighter to the fan just to get it to run but it only ran on high. You can get a lot more heat from a 300SD if you leave the fan on low on cold days. Fixed that problem with a rebuilt climate control, but...

For over a year now I only get heat if the heater is on and the thermostat high when I start the car. If, while driving, I turn the thermostat down then it blows cold and in order to get heat again I have to stop and shut off the car then start again with the heat on. This problem was there with the old control and with the rebuilt control so I suspect that is not the problem.

Once on, the heat will stay on until I turn off the car or turn it down. You guys think this could be the valve? I've had my valve go before but these symptoms seem different.

What about the sensor above the windshild?

Any ideas?

Brian