Lifetime Premium Member
Date registered: Oct 2002
Vehicle: 1967 250 SL, 1963 220Sb
Location: Los Angeles / Altadena
Mentioned: 3 Post(s)
Quoted: 102 Post(s)
Hi. I just replaced the climate control unit on my 1984 300d with a new replacement. The buttons work but the temp control wheel only changes the temp for heat when it is clicked into the high setting. In other words, the climate control doesn't work. I have heard about the interior sensor behind the glove box and the duct leading to the sensor as possible culprits. I have also heard that it could be the heater control valve. Any help would be appreciated.
1. What was wrong with the old one?
2. One reason the control units fail is because the aux water pump frys, too much current goes to it trying to make it pump, the current goes through the control unit, the control unit then fails. The point of this is to verify that your aux water pump is working (turn key to on but don't start, you should be able to hear it if you stick your head under the hood). If pump not working, unplug it or you will fry your new control unit. If pump IS working, add a 1 amp in-line fuse to it so that if it fails it desn't fry your control unit.
3. Are you saying that heat is always OFF unless you turn it all the way to hot? If so, I would suspect the interior sensor. take out glove box and replace damaged/missing hose that goes from the little grill in the center of your dash top to the right side behind the glove box. Using pipe insulation as a replacement tube works fine.
4. Does AC compressor come on?
Those are the starting questions to answer before you proceed...
Currently: 1967 250 SL, 1963 220Sb, 1965 300SE Lang, 1971 280SE parts car, 1972 Alfa GTV, 1965 Alfa Duetto, 1993 BMW R100R
Past: 1971 250 C, 1985 300 TD, 1967 250 S, 1968 280 S,1981 300 D, 1982 280CE, 3 Facel Vegas, Borgward Isabella Coupe, Alfa 2600 Sprint, Volvo P1900 (yes), numerous less interesting Volvos, ...