I have a '93 300E and have recently been having issues with the climate control. Before this, it's always worked perfectly (as far as I could tell, anyway).

A couple of days ago we got into the car after some shopping and the climate control would do nothing but blow cold air, no matter what settings were tried. We turned it off for about 15 minutes and when it was turned back on it was fine. Over the past couple of days it's hasn't done anything that bad, but there have been times where it feels like it's malfunctioning before quickly starting to work again.

Any ideas how I'd go about diagnosing this? A search of the forum find that there are a lot of vacuum problems with these systems and I'm thinking it might be something along those lines but I'm not sure.

Thanks,
Mike

Anyone have any advice? Thanks.

Hello,

My two cents worth...............

Turn the temp dial to hottest setting.
If its blowing cold air only, check the heater valve [on/off] and the aux water pump.

The aux pump can fry your climate control unit if its been sticking etc, draws to much current. Bad design really considering this runs most of the time.

They should have installed an aux relay to control the aux pump and the heat valve.

You can feel if hot water is going through both of these.

good luck

Brian

Thanks so much for your help. Next time it acts up (which is likely to be soon) I'll check that out.

Thanks again.

-Mike

It is easier to just unplug the duo/mono-valve. If it has no power, it is left constantly open.

This, among the literally 15 other issues that I had with my 300E was the reason I finally decided to sell it. I just didnt see it worth the time and effort to put in $3500 to fix the problems on a car whose actual worth was $3000 in retail. Not to mention even lower in wholesale.
Sooner or later these cars tend to be nothing but a money pit. If you "love" this car keep spending money, otherwise, trade it in purchase a newer w210 model and use ur time enjoying while driving rather than staying home and fixing.

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