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controlling temperature

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1991, 190E 2.6L From a cold start of the engine, as the temperature raise-up. Outboard outlets will start shooting warn to hot air. Using the wheel temperature control on dash trying to lower the temperature will not stop hot air to cool down (right away) until it reaches the highest mark on the wheel, just before it forces the air conditioning process to engage. At this location it will take long before the temp. cool down to normal. RARELY cold, even if the control wheel is set at cold spot and air conditionning is always set to "on" position. Any ideas where i could start looking to investigate. Thx!
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280SL Pagoda, BMW318
98 Posts
unfortunate result of US market gimmick :-(

Unfortunately yours is a common an not inexpensive problem with these cars. These systems are very hard to diagnose by the DIYer - you are best taking it to a Mercedes specialist to at least get them to tell you what the problem is.

If you are lucky, it will be the control panel (where the wheel and buttons are). This shouldn't set you back too much.

The less fortunate option is that the potentiometer is buggered. This is the little motor that opens and shuts the valve for cold/hot air. While the part is all of about $40, the whole dash will need to come out to replace it. It cost me about $1500 for this repair [:0] (including aircon recharge), and it took the repair shop (a very reputable MB repairer) 2 goes to get the diagnosis right (so imagine how long it's going to take you!).

There are other possibilities, but these are your most likely I think. Other people may have better input to this discussion.
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