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  #1  
Old 06-27-2007, 12:46 PM
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92 300d front fans not working, running warm.

my 92 300d has been running pretty hot, between 85-95, and the front fans have not been working. i just bought this and the front 2 fans in front of the radiator have not been working since i got it. the previous owner did say he disconnected them sometimes in the winter. i cant get a hold of him, anyone know where to find the connection?

also, is it hard to replace the thermostat in these?

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  #2  
Old 06-28-2007, 07:57 AM
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Do a search on 300D (W124) cooling problems. There are quite a few threads on the subject. The 124 body style has a tendency to collect bugs behind the fan motors and quit working. The plug in for the fan are on the right hand side (as you face the car) behind the front headlight. Check the fuse also and verify that both fans work.

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  #3  
Old 06-29-2007, 05:35 PM
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i looked behind the headlight, it looks like a black plug? i think thats it, the wire looks like is going to the fans. its plugged in. i dont know where the fuse is located.
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Old 06-29-2007, 08:07 PM
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If it's running between 85C and 95C, the electric fans are not supposed to be running, I believe that they come on at 100C or 105C, check the FSM. The engine-driven clutch fan should be starting to work around 95C (from memory).

With the A/C running, if there is sufficient refrigerant charge (pressure) the fans will run low-speed.
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Old 06-30-2007, 01:28 PM
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so what is the normal operating temp with ac on and ac off?
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Old 06-30-2007, 02:10 PM
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The aux fan should come on low speed when a/c is on as long as ambient temps are high.
A quick test for fan circuit is to jumper the high pressure sw at the drier [ the one with the pigtail wires].. Just peel back the sleeve at the white connectors and jumper there w/key ON..that will give you Low fan..High fan test is to disconnect/unplug the engine coolant temp sensor [ 2 wire/blu one-105C.], That will default the ACC unit to High fan.
If both these test work, you have verified fan circuits integrity, BUT..if you never see a Low fan activation and it has passed the jumper test, then you can be slightly low on refrigerant..[ low ref. will not produce s high enough high side pressure to trigger the sw ] Very common mis-diagnosis...this condition will be coupled with a complaint of poor a/c output at stop/idle
If either of the fan speeds fail these test, the first place to look is at the fuses.
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Old 07-01-2007, 09:59 PM
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The second place to look is the speed resistor. I've never lost a fuse, but I've had two bad resistors.
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Old 07-02-2007, 11:39 AM
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where exactly are the resistors located? im having a hard time locating them.
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Old 07-02-2007, 12:09 PM
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Quote:
Originally Posted by BulletHead View Post
where exactly are the resistors located? im having a hard time locating them.
It is a single resistor.
http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=23I0RAMEE24G0PWPHQ&year=1992&make=MB&model=300-DT-003&category=G&part=Aux.+Fan+Resistor
Look behind the left headlamp.
Did you do the simple jumper test I posted? That test is low fan with resistor, so if you pass that test, you do not have a resistor problem.
You should do the test ...
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  #10  
Old 07-02-2007, 08:51 PM
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i definitely dont have enough refrigerant, ac isnt quite as cold as id like it. im going to have to do the resistor test to verify other possibilities, thanks all.

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