1994 320E wagon

My auxillary fans only come on when the temperature almost reaches 120, When the air conditioning is on there is apparently another sensor that also operates the auxillary fans so that the temperature
doesnot get this hot. Does anyone know what that sensor is and where it is located.
Thanks
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High pressure switch for low fan is located on the reciever/drier.. Jump it to see if you have fan..
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If your car is running A/C and the engine is at least 80 degree, you should hear the aux fan come on and off. If not, I suggest you look at the aux fan relay in your fusebox... kinda a pain to get to, you have to loosen 6 screws to get to the relays... it is the fuse box cover that you must remove to get to the relay... blue one with a fuse I believe.
I just did this on mine... fan doesn't come on low or high... turned out to the fuse on that relay was burnt out.
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The reason for jumping the a/c high pressure switch is this is the first step to diagnosis on this 124.032 system. This quickly checks the integrity of the electical circuit for low [a/c ] fan. If the fan does not come on, then you go to relays,fuses, dropping resistor, etc... This test takes all of 20 secs and will tell if the problem is theelectrical circuit or freon pressure related. If the fan comes on w/jumper , then you have a good relay. fuse, resistor, fan circuit. In which case , the problem is that the high side a/c pressures are not getting to cut-in specs [ 20 bar] to turn the circuit ON.. This can be a bad sw., but the most liely culprit is you have a shortage of freon charge- thus not enough high pressure to trip the fan circuit. Remember this when diagnosing fan circuits on 124.032: There are TWO completely different circuits for the 2 speed aux fan. They each have their own fuse/relay/ and sensor circuits . They just share the SAME fan motor. The high fan is tripped by the 2 wire thermistor sensor at the thermo housing and it is set to trip at 105C , collant temp. This is the blue relay. The a/c low fan circuit is tripped by the high pressure of the a/c compressor system and has NOTHING to do with the high speed coolant temp sensor circuit. It consists of a relay,fuse, high pressure sw. and a dropping resistor [ behind driver headlamp]. SO.. no low fan, you are in the a/c pressure activated circuit.... No high fan, you are in the Engine coolant temp senor circuit. Also, Benz had a TSB fuse change on this chassis allowing up-gradeing the 15 amp fuse on the coolant temp relay to 25A....
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It didn't work on my 95... I did everything to get it running... the only way I got it runnning is by pulling the wire harness off the two prong (blue) thermoswitch for high speed aux fan.
I have done it... by connecting the two wires together at high and low pressure switches... nothing for aux fan... compressor was working fine as it was regardless of both switches... because I did have freon.
This crude method just doesn't work for any digital climacontrols that MB uses now... it would work for analog systems... still that fuse on the aux fan relay really does shut power off to the aux fan.
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That is test for HIGH fan circuit ONLY When that sensor /thermistor hits 285 ohms , it trips the relay.The post is adressing the a/c aux fan, not the coolant temp fan.

Which means you have a bad relay. fuse , or dropping resistor for LOW fan. There is another realy and fuse for 94/95- 124.032 . This is the green realy in slot #2.

which is what we are talking about..
still that fuse on the aux

The HIGH fan, not the low [a/c fan..] Reread my post and see that there are TWO relays w/fuses on top. One for high and one for low One is in slot "B' and the other is slot "C" Check the schematic and you will planely see both circuits. If the low fan does not run with high pressure sw jumper , the problem is in the low fan circuit [ most I run across is the fuse on the low relay or a burnt wire on the voltage dropping resistor.---very common

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