Thanks, folks, for your comments and advice. I have added my 1983 300D to my signature line. I realize that it is activated by A/C pressure, and as the previous posts indicate, we are attempting to determine whether the fan is faulty or the relay. I have already disconnected it from the Receiver/Drier, and attempted to connect those two wires together, but all I got was clicking from the fan relay. The suggestion was made for me to wire it directly to the battery in order to see if it would come one, and I had to find the connector in order to do so. I won't have time between now and Saturday to jack it up and look for the connector, but I hope to do so Saturday. If it does turn out to be the fan, I found someone who is selling one for $25.00, and I need to determine whether or not it is the fan before purchasing that one.

Thanks again, and any and all other suggestions are welcome!

The fan switch is a temperature switch, not a pressure switch.

That would be factually incorrect.

The connector is a little tricky to find. It is roughly at the lower, left corner of the oil cooler. You can see it from the left wheel well. It's about the size/shape of a cigarette lighter (the old "box" style) and is just forward of the left-hand horn, clipped to the frame.

The fact that you hear the relay clicking is not a quarantee that it is working, but it's a pretty good sign. You could switch relays if you want.

Well folks, I had a chance today to disconnect the auxilliary fan and hooked it up to jumpers straight to the battery, and couldn't get it to turn, although it turns freely by hand, so I guess that pretty much proves that the fan is not working.
Any other suggestions?:confused:
Has anyone had luck rebuilding these fans? I read somewhere about rebuilding them, but don't have a source for brushes.

Thanks so much!

Well, to close the loop, I had purchased a fan on eBay, and it arrived today. When it arrived, I plugged it in, shorted out the two wires going to the receiver/drier, and it fired right up! With the help of my son, I installed it, drove around awhile, then had to let the car idle ~15 minutes before the fan kicked in, but when it did, it really roared!
Boy, that bottom bolt is a pain in the rear!
While the fan was out, I took the opportunity to examine the condenser. I couldn't believe how many little rocks and crud had gotten between the fins, so I blew out the condenser with water and air pressure, before installing the new fan.
Works great, and thanks again for all your help in troubleshooting and isolating the problem to the fan!