560 sl electric cooling fan
 

I checked for threads but couldn't find one. The electric cooling fan on my 560 never comes on. I hooked the fan directly to a 12 volt supply and it worked fine. I'm guessing there is a sensor at fault. Anyone have an idea which one and where it's located. Thanks

should be a sender off the block? they are usually rated at 100C

There is another one on the AC receiver/drier.
Measures refrig temp.

Rowdie's post jarred my memory about this switch and circuit...

On my '87 560, following the wire from the receiver/drier over and up the passenger side of the radiator, you'll find a ceramic resistor that due to it's location fails quite often. You'll know if it's bad simply by squeezing it between your thumb and fingers; if bad it will crumble. Or check with voltmeter on either side of resistor to be sure. Replacement is very inexpensive, and easy.

Bob

I actually looked at that resistor. Any idea what it should ohm out at?

I'm sorry, but I don't. Perhaps someone that has a 560 can measure theirs for you. That resistor on my car was so far gone it just crumbled. Once again, it's very inexpensive to replace.

Bob

aux fan
 

I checked the ceramic resistor,it did crumble. I replaced it,still no fan working.checked fuses,all ok. the temprature switch on the engine has three post one connector goes on two of the post, another goes on the remaining post.I unhooked the two post lead and jumped the wires. nothing happened.thanks miker:D

Do you have a manual? If not... http://www.startekinfo.com/StarTek/outside/11883/?requestedDocId=11883

In it, you will find the following diagram (and a host of other info). The Aux fan is controlled by two inputs: Coolant Temp, A/C pressure. The resistor is only for the A/C circuit. The coolant temp provides full voltage, when the temp sensed is above 105C... The other side of the temp sensor is to cut off the A/C if the temp gets to 115C.

aux fan
 

I took some time, but I have figured why my aux fan would not work.there is a switch on the drier that is partly red in color disconnect the two wires start the car. the fan sould be running.you will have to replace the switch.Im not sure if it would loose the freon if you unscrewed the old one.you may need to take the car to someone that can save the freon. give them the new switch and have them replace it.then put back the freon,and check to see if it needs more.good luck miker:D

forgot jump the two wires this should make the fan run

Yep... Shorting the wires will force the fan to come on, just like a high pressure on the drier (consult the wiring diagram), but this does not prove the fan will function properly. Shorting the wires together does prove the relay for the A/C drier pressure is functional if the fan comes on, and it also proves the resistor is not open.

I suspect an aux fan relay is faulty in the OP's post. Otherwise, wiring is suspect. Since he jumped the contacts on the temp switch and the fan did not run, I suspect the relay. The fan will work independent of the A/C circuit (once again, consult the wiring diagram), and vice-versa. The two circuits are essentially separate. The A/C pressure switch routes the voltage thru the resistor, but the temp switch does not.

And according to recent discussion on another board, if you do change the switch on the drier, you will vent freon...

Question: When do you expect the auxilary fan to be on?

need help located aux fan relays
 

My aux fan also is not operating. Can someone please guide me further?
To test if the fan itself works, I just need to jump the 2 wires on the red switch on the drier? With the engine running?
I see the aux fan wiring diagram in this thread showing both a aux fan relay and an aux fan preresistor relay.
Where are these relays, in the front of the engine compartment or in the fuse/relay box inside the passenger compartment sidewall?
The wiring diagram for the fuse box/relay box only shows an aux fan relay for RH drive cars.
I tried tracing the wires back from the resistor and see only these odd looking devices (see attached picture) but an not sure what they are. Are they relays? If so, do I open them up? How to I change them?
I would appreciate if someone could point me to the aux fan relays.
Thank you