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  #1  
Old 09-06-2003, 01:44 AM
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Location: CA
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Help: My Aux fans don't work

I noticed today that my temp went up to almost 110. I turned off my AC and popped the hood. I noticed that my aux fans don't work. Can anyone help me with this. I checked the fuse box in the engine compartment and all the fuses are fine? Is there something else I need to check?

I'm desperate coz I'm scared to drive my car (W202) far.
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  #2  
Old 09-06-2003, 08:39 PM
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Location: Tucson, Arizona
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Keep your cool

Greetings,

What year and make car are we talking about? On several models the cooling fan is controlled by the temp switch in the a/c system. This switch is generally located by the a/c condenser in some case is green and is threaded into the side of the reciever dryer housing. If you want to do a quick check of the fan itself you can use a paperclip and close the circuit between the two wires. If the fan comes on, then most likely it's the switch that has gone bad. If your temp goes that high with the a/c on, where is it without air? You may suspect the thermostat as faulty as well as the flow of coolant through the system if you end up with a puddle in your driveway while it's running. Are you losing coolant? Look at these few things first and give a few more details on the car we are troubleshooting.

Charles
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  #3  
Old 09-07-2003, 08:45 AM
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Start with a search on "aux fans." You'll find a wealth of info since this system often seems to break down. The plus side is that it's an easy system to troubleshoot and fix.
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  #4  
Old 09-07-2003, 11:16 AM
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Join Date: Jan 2001
Location: N.PALM BCH
Posts: 41
-follow the fan cable to a plug. jumper 12v dc to the cable to see if it runs. if it does then the problem is on the a/c drier pressure switch
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  #5  
Old 09-07-2003, 02:11 PM
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Location: Florida / N.H.
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Quote:
Originally posted by 400E
Start with a search on "aux fans." You'll find a wealth of info since this system often seems to break down. The plus side is that it's an easy system to troubleshoot and fix.
Ditto..

Also, to save some common possible mis-diagnosis , ie- low fan switch..

The common practice of jumpering the a/c drier high pressure sw. and looking for low /ac fan operation is NOT a switch test...
It is a quick tech trick to verify both the fan Motor/s and the integrity of the low fan circuit [ fuse.relay, dropping resistor, etc]
This test tells the tech that the fan motors of BOTH high/low circuits are Ok as both circuits share the same fan motors.
SO, if you get low fan when jumping, then condemning the sw is way off the mark... There is a way higher possibility of the a/c system being low on freon [ not enough freon pressure to trip the switches cut-in spec.]
It is also possible to have NO low fan called for at low amient temps. The fan is there only to help/assist controlling high side pressure [when they are triggered by high thermal load]
The ONLY way to test the high pressure sw is with gauge reading of the high side pressures and comparing the readings to sw specs...
Quick fan motor/circuit test ? -Yes..
Switch test ?.. No
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  #6  
Old 09-08-2003, 02:12 PM
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Join Date: Jul 2003
Location: California
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Thank you to everyone who replied. I tried testing the low switch (by the dryer) and the fans didn't work. Just when I was about to give the fans a 12 volt, I realized that I haven't checked the relays yet. Being a newbie to benz cars, I had to research where the relays are and eventually found it. Luckily I saw that 2 fuses on top of the relays where blown and therefore just simply replaced them. Now everything is fine. The question that bugs me though is what caused it.

Again thanks guys.
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  #7  
Old 09-08-2003, 02:15 PM
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<
>>

Benz has changed the Amp rating to 25 for high fan, from 15......
low is 30...
Common to blow the orig fuse set-up
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  #8  
Old 09-08-2003, 03:03 PM
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thanks for the info. I'll go and change them today.
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  #9  
Old 09-10-2003, 01:54 PM
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Join Date: Oct 2002
Location: Texas
Posts: 303
check it out

check out the cool harness. it might help you. It did me


http://pages.prodigy.net/jforgione/MB_S500.html

Best of luck
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