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Engine Fan Visit Workshop

9K views 3 replies 2 participants last post by  mrboca 
#1 ·
Ok, so I am new here, please gently let me know if I posted this wrong
My 2000 E320 HAD a problem with the A/C EC light. My mercedes mechanic mechanic told me that I needed a AC Controller under the hood. But it is in the car DUH! Second time in 3 years I was told that the controller needed to be replaced.. BUT I reset the controller and it works GREAT but three days later the Engine Cooing Fan isn't working with message on the dash. I have replaced the temp sensor, Checked the fan with 12v and it works, swapped out a couple of relays. When it gets hot I get the message and when I turn on the AC the fan will not work.
PLEASE HELP!!! I cant afford to pay someone to misdiagnose it no more!
And being that I am a pretty fart smeller, I KNOW that I can fix it.
I do not know if there is anything that is vacuum controller for the fan but it has been running ever so slightly rough like a vacuum leak.
I do not want to do it but I am about ready to put a temp sensor on the radiator hose, relay etc.. but my nae is NOT Jerry Rig
help!
 
#2 · (Edited)
Hello and wellcome :)


When the mechanic mentioned the A/c controller, I think he mentioned the A/C fan controller which is a unit under the hood. The N76 module in the picture drives the fan which is both cooling the radiator and the a/c condenser.

If the fan does not run at all (when the engine coolant temperature is high and / or the a/c unit is turned on and cooling), then it could be the N76 module or the SAM (N10/1 in the picture). The fan in the picture has a variable speed so there is really no relay to control it at different speeds. I would also check the fuses on the SAM to make sure it is not a fuse issue.

Just to make sure.. Please confirm that you have only ONE electric fan between the radiator and the engine, not two fan units (visco fan plus the fan unit IN FRONT of the radiator/condenser)
 

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#3 ·
Engine Fan Visit Workshop E320



Thank you for the prompt reply. In my process of elimination I started out by changing the Fan Controller Unit when the AC was not working and the fan was. I even swapped it out to see if there was a change, but no. Then i changed the temperature sending unit near the thermostat housing. My E320 just has the one big fan (My biggest fan) :) on the passenger compartment side of the radiator
 
#4 ·
If I understand the problem correctly:

1) Your cooling fan does not run at all to cool the engine or the a/c condenser unit.
2) You leave the engine running in idle while observing the temperature gauge, the gauge climbs above 95, and the fan does not come on at all
3) You turn the a/c unit on in cooling mode, and you press the both AUTO buttons at the same time for at least 15 seconds, and the fan does not come on.
4) you replaced the N76 fan controller module in the picture with a known working module and it still does not turn the fan motor.
5) fuse#20 at the driver's side fuse panel and it is not blown (powers the N76 controller)
6) you have battery power at the N76 connector pin number 3 ( thick red/black wire) (from fuse #20).
7) You checked the connectors at the driver's side fuse panel and the SAM unit.

Do you have any check engine light on ?
 
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