Question about auxilliary fan not working
 

Folks, I just got my AC fixed after going without all summer, and realized this evening that my auxiliary fan didn't come on. First thing that I'll do tomorrow is to check the fuses, but the fan turns and is not bound up. This is on a 1983 300D. Is there anything else that I can do to troubleshoot this issue? Thanks so much again for your help!

Aux fan is on a temp controlled thermostat located by the pass. headlight, on top of the A/C dryer.

If that switch is bad, it's not going to come on.

Also check Fuse 14/16 in your fusebox, that controls a lot of relays.

(If your thermo switch is bad, I have one for sale cheap that I don't need)

Disconnect the two wires at the temp sensor on the receiver/drier. Then connect the two wires (the ones not attached to the switch) together. The fan should run when the key is placed in the "run" position.

The temp switch looks like this:
http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=2650Q36L326X0CCT0A&year=1983&make=MB&model=300-DT-001&category=R&part=A%2FC+Temp.+Switch

Thanks so much, folks, for your help. I'm going to take a look at things this morning and will get back with you, thanks again!

i leave my 2 wires connected together all summer deathly afraid of overheating

Thanks so much again, folks, for taking the time to reply to my question. I didn't have a chance today to check into the fan, as I was busy replacing the overflow tank, flushing out (as best I coulde) the radiator and refilling with fresh antifreeze and Water Wetter, then installing my ipod adapter for my new car stereo and putting everything back together again. Tomorrow I am going to try the wiring trick with the auxiliary fan and hope to change out all of the fuses for new ones. Thanks so much again!

Well, folks, I had an opportunity to look at the wires going to the receiver/drier today, and before I do anything that I regret, I thought I'd double check with you all to ensure that I disconnect and connect the appropriate wires.
I have two sets of wires going to the receiver/drier; a blue and a brown wire, going to a switch located on the top of the receiver/drier, and a green and blue striped wire and a blue wire going to a switch located more to the side of the receiver/drier.
Which set of wires do I disconnect, and which do I connect in order to turn on the fan?
Thanks so much in advance for your help and patience!

You want the one on the very top. The wires connect to pigtails from the switch, not to the switch itself. (On the other switch, the wires connect directly to the switch.)

Once the two wires are disconnected, take the two that are no longer connected to the switch and connect them together. That should cause the fan to come on with the key in the run position. The a/c need not be on.

qft, it can't hurt anything.

What's the CFM on the Aux Fan vs. the Main Fan? I feel like the main fan saps too much power, and was thinking of converting it to an electric, or getting a dual aux fan setup and just using that.

Nothing but the fan.

Well, folks, I did what you suggested, and the fan did not come on. As I placed them together, I heard a kind of clicking noise over by the fuse box, so I removed the fuse box cover, and did not see any blown fuses. Over the weekend I replaced ALL of my fuses, as I'm sure some of them were original to the car. At any rate, the fan didn't come on, I could see no sparks, and I don't know where to look next.
Any ideas or suggestions would be GREATLY appreciated, Thanks so much in advance!

The clicking sound would have been the fan relay, located under the plastic cover on the inside of the left fender well.

If you trace the power cord from the fan, you will find a connector. Unplug the connector and connect the fan directly to the battery.

Thanks, folks, for your suggestions. This evening I looked at the wiring harness on the Aux fan, and it looks as though it goes under the engine compartment under the windshield washing fluid cannister, but I don't know where the connector is to disconnect it from the rest of the circuit, in order to just connect the fan straight to the battery to isolate whether or not the fan is bad or perhaps the fan relay is bad.
Any suggestions?

Thanks so much in advance!

It would be great if you would enter your car year & model with your signature.

You will find the fan connection behind the lower cowl on the drivers side. A zip tie was used on mine to hold the harness to the cowl on the side (of the connection) opposite the fan. At least that's where my '84 location was. You will probably have to turn the front tires out or raise the car to access the connection.

And this fan is triggered on by A/C pressure not simply that the compressor engages. So, if ambient temperature is not real hot the fan will not come on for some time. It is also triggered on by engine temperature thru another circuit, so again, if engine temperature is stable within range, the fan will take forever to turn on.