I have had my car for about 6 months. I tried the air conditioning, and found it did not work. So, I took it to a local air conditioner man, and he charged it up. In the process, at no time did the condensor/radiator electric fan come on. I do know the fan will run if the motor heats up while idling and then shuts off. What can I check to see why the fan does not run while the air condtioner is on?
Thanks.

It sounds like you need to check the function of the pressure switch. It is located on the drier bottle behind the driver's side head lamp. There will be a switch on the bottle that is either green or red with two wires coming from the switch. Find the connectors that are about a couple inches away and bridge them with the key on. IF the fan runs, your switch is faulty, if not, there is a problem in the curcuit.

Benzmac....... I did what you suggested and nothing and the fan still did not come on. I got out a manual I had, and it said if I didn't have a new relay to put in to check it, to do this...... which was remove the relay and jump across the #30 and the #87 on the relay socket. I did that, and the fan came on. So, it said I can assume the relay is bad. But, how can I really check it out? The relay may be fine, but something may not be activating the solenoid to make contact. What else can I check? Or is the relay in fact bad? Many thanks.

I would like to add that I am approximately 200 miles from a Mercedes dealer, and I really don't know of anyone close to where I live to work on them. I live in the boondocks. I used to work on major home appliances, so I am reasonable familiar with tracing out things if I just know where they are and what items to check.

[Edited by Ron Miller on 04-05-2001 at 01:32 AM]

I have discovered that the aux. fan dropping resistor is burned out, the one right behind the left headlamp mounted on the fender. Does any one know the ohm value and the wattage rating of this resistor? Thanks.

Well, I got my air conditioner aux fan working properly, that series resistor was burned out. I couldn't get the parts fastlane to let me buy a part, I mean I would click on buy, and nothing would happen, and nothing was in my shopping cart at checkout. I had tried to get a part somewhat local, but no one has any benz parts in my neck of the woods. So, I got one from another source, but I really wanted to get my parts here. What am I doing wrong for the online buying?

Pressure Switch
 

I had this same problem except jumping the green switch made it come on, does the refrigerent have to be taken out to replace this switch or is there a schrader valve underneath it? I have heard I should change it to the red switch as it comes on sooner?

BigRichard72@home.com