Hello!

I have a 240D W123 1983 (I think)
The Aux fan does not work I even left the AC on and the car running standing still for 15 minutes and its no good, I know the fan is good (I ran a positive wire to it and it ran)

It gets quite hot here in Sri Lanka and the AC does not seem to do much cooling with the fan not working, this is my dad's new car, its new to me so I'm not sure where the components are located
If you could tell me where the relays/sensors are located I can test them and pin point the problem
I've mostly worked on the /8

Thanks

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1975 240D W115 version 3 (Australian car )

PS: I meant I think in terms of the year LOL

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1975 240D W115 version 3 (Australian car )

The earlier W123s have a black box on top of the left wheel well in the engine bay, which contains the aux fan relay among others. The later W123s have a different set up and I'm not sure where the relays are, however, it's rare that these relays fail. Since you know the fan works, I would check the plug connector from the fan lead to wiring harness. Sometimes these connectors get enough crud in them to stop a connection. It's located behing the front valance, very close to the left horn.

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Don't Chrome them; polish them

I found the black box,
Doesn't it have two sensors?
where are they located?

Thanks
Jeremy

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1975 240D W115 version 3 (Australian car )

Hi

I just removed the wires that go to the ac sensor and ran a wire across and the fan ran with the relay clicking!

So I guess that sensor is faulty, could you also tell me where the sensor is for the engine temperature that turns on the aux fan as well?

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1975 240D W115 version 3 (Australian car )

http://catalog.peachparts.com/ShopByVehicle.epc?q=&yearid=1983@@1983&makeid=63@@MERCEDES+BENZ@@X&modelid=6143%3AED%7C10000129%3AMBC%7C1489@@240D&catid=242213@@Climate+Control&subcatid=242240@@A%2FC+Temp%2E+Switch&mode=PD

I don't think there's an engine or coolant switch for the aux fan, it's only triggered by the switch on the receiver-dryer.

If the A/C isn't running correctly (e.g. compressor not working, low on refrigerant, etc) then the R/D won't get hot and the fan won't turn on. Does the "black box" (more like a cylinder in my opinion) get hot? If not, then the switch may or may not be good.

I think there are also different temperature switches for gas and diesels. You could carefully unscrew the sensor and test it in hot water with a voltmeter. Check the temperature at which it closes. It's possible that everything works but you've got the wrong sensor in there. Be careful re-torquing the sensor back into the R/D since the threaded end is a bit fragile. It doesn't have to be super tight since it doesn't seal the system, just tight enough to conduct heat from the R/D into the switch.