I know there have been many discussions on this forum about these fans, but I have been unable to find any comments on my problem.
Mine were not working and I replaced them. The replacements work when I do the "Hold the auto buttons" in procedure. They do not work when I run the A/C. I get cold air until the compressor shut off because the Aux fans do not come on.
Any ideas or other checks I could try?












c

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1998 E300Turbodiesel
1980 300d

Ready- Ronnie

MattL once posted that the chinese AUX fans came wired in reverse.

Confirm they spin in correct direction.

Ought to be getting a CCU AC code too if the compressor shuts down.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

Thefans I installed are used from a Mercedes. I will run a code check. Thanks

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1998 E300Turbodiesel
1980 300d

Ready- Ronnie

I had a similar A/C issue. It had me pulling my hair out. A/C would work for a bit then shut down, or work at lower level of performance. Finally found that the accumulator drier had debris in it from a previous A/C repair. Flushed the system and replaced the drier. Works like a champ. Indie says you should be able to blow through the drier inlet with no restriction.

Hopefully this will be of help.

I ran a code check and did not have any code registered on the OBD scanner
I found that with the A/C running I could also make the Aux fans run by pushing the two auto buttons.
I would like to try the dryer flush that was suggested by bucksterdad, but have no idea where it is located of how to do it.

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1998 E300Turbodiesel
1980 300d

Ready- Ronnie

This is pure speculation on my part, based on my observations. I believe that the aux fans run based on the AC system pressure. If the main engine fan is working properly and pulling plenty of air through the condenser, then they won't come on.

If however, the air is hot coming through the condenser, the system pressure will increase and the fans will come on with a speed proportional to the pressure.

I've never been able to test this theory on my car because my main fan clutch is bad and the aux fans run all the time. I would think you could induce them to run by blocking the air flow through the grill while the car is idling and hot.

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-Evan


Benz Fleet:
1968 UNIMOG 404.114
1998 E300
2008 E63


Non-Benz Fleet:
1992 Aerostar
1993 MR2
2000 F250

KarTek is right in that the fans turn on and vary speed based on the system pressure - but also based on engine temperature. There is a controller for the fans bolted to the left side frame rail, below and behind the left headlight. I replaced my fan motor but it only ran at about 5 rpm...the old one must have caused the controller to fail. Don't know if that's your problem or not, but it could be. Controller is VIN specific and costs about $200 if I remember correctly.