New to the forum. Am not at all tekky: switch on and steer is the limit of my knowledge. Help me please. I have a 1986 230E only 93k miles. Bought it three years ago and have always had terrible heater problems. Comes on and off at will, twenty minutes of heat often then v cold for hours on long journeys. Stop car, switch off and restart often gives heat again for another ten minutes, etc. Drove across Europe 1600 miles each way in winter several times with this problem. Have had duovalve (?) replaced twice, neither of which did any good at all.

Are you saying I need to get something flushed out, and this might solve my problem. Have printed out your entries, and will take to mechanic. Grateful for your advice if you think solution proposed in your entries will also solve my problem.

Otherwise my car is excellent and the best purchase I ever made.