Blower Relay?
 

To all the experts,

I am working on a 1992 300E with a heater blower problem. The controls are fine, the blower it self is fine, the regulator underneath is fine. What I found out was from the blower connector (3 wires), the red wire is not giving any juice at the connector referred to in (1) below. If I jumped the line directly from the battery, everything seemed in order. It could be anything, but does anybody know:

1. If the black male three-pronged connector (bolted down to the firewall) is some kind of resistor device? How do you remove it for checking? Does it require getting inside the dashboard?

2. Does the blower utilize any relay? If yes, where is it located? If inside the relay box next to the main fuse box, which one is it?

3. Any hint as to why this outtage is very much appreciated.

Thank you.

What are the symptoms of your problem? The blower on my 89 300E works fine on low speed, but I have no high. Wondering if it is the same problem.

Sounds like a cracked fuse to me. There should be a single metal strip style of fuse in a black holder about 3/4 inch by 2.5 inch located forward of the fuse box.

The three wires you are looking at should be yellow red and brown. The red is the main power and comes from that fuse. The brown is the blower ground and the yellow is the control signal. It starts low for low speed say 1v and grows to around six volts for "MAX". The signal comes from the pushbutton controller.

BTW the cracking of the fuse is a wear and tear item. The current warms it and it flexes. The cycling cracks the fuse over time.