jehovden

Hello all!


So I've had a thread going about my AC not cooling the air until after I have been driving for several minutes.
Many tips pointed at the big fan behind the condenser radiator, and I have found out that this one is not starting/running as it should (as in never at all).

Yesterday I took out the fan and hooked it up to my friends car just to see if the fan is working at all. Kinda hoped it was not, because then I would have located the problem. Then fan was working however..... On his car the fan started as it should.

So the fan itself seems to not be the problem.

Anyone with experience that could tell me what to look for next?
I have been looking over the fuses and all seems to be in order. Since my german is not that good I do not know the specific fuse i should look for though. Anyone?

Any advice would be highly appreciated!!

530inOK

According to WDS the fan's fuse is F9, 60A in the front fuse holder behind the glove box. I'm guessing it's probably ok since your fan is good. The IHKA (A/C controller) and DME are in control
of the fan as described in the caption below. For some reason I had saved this image of an A/C Pressure Safety Switch. I'm not sure if it's the same as a refigerant pressure sensor described
below. Maybe it is a sensor/switch that has failed as Ricracing described in your other thread.
Keep us posted as to what you find out. As these cars age we'll probably see more and more of this type of failure.
Good luck!!


E60, E61, E63, E64 - Auxiliary fan
How it works
The auxiliary fan cools the condenser. The auxiliary fan is switched on at road speeds below 70 km/h (approx. 43 mph). The
auxiliary fan is switched off at road speeds above 80 km/h (approx. 50 mph).
At higher speeds, the air stream alone is sufficient to cool the condenser. At lower speeds and when stationary (idle), the cooling of
the condenser must be supported or maintained by the auxiliary fan.
The speed of the auxiliary fan depends on the refrigerant pressure. Speed is regulated as follows:
- The refrigerant pressure sensor sends a signal to the IHKA control unit that is linear to the refrigerant pressure.
- The IHKA control unit calculates the fan speed needed for the auxiliary fan. The 15 possible fan speeds are assigned to
pressure values in the refrigerant circuit. This demand is transmitted by the IHKA control unit through the body CAN and
powertrain CAN to the DME/DDE.
- The DME/DDE control unit regulates the speed of the auxiliary fan with a pulse-modulated signal (PWM signal).
The maps for the auxiliary fan are encoded in the DME/DDE control unit. The encoded map for the fan (encoding viscous fan
coupling or electric fan) always gives at least speed 1 when the air conditioner is switched on.

jehovden

Hello,

And thanks a lot for your feedback!

I have checked the fuse, and "of course" this was not the problem it seems. Would have been too easy I guess

From the above it seems like you really know what you are talking about
So it appears that for some reason my fan is not getting a run signal. It sounds almost impossible for me to find out why, or where the signal stops...
Is there any futher things I could check my self before bringing this to the dealer?
And what will the dealer do? I bet something like this does not appear on their diagnoses tool/computer as an error code, will it?
Smells like an expensive ordeal...

By the way, what is the small unit that is clipped on top of the fan? Small plastic thing with three thin wires coming from the same wire-harness as the wires for the fan. From the part catalogue I have it is called something like "AUC sensor org Klimatautomatik". Any idea what is the function of this?

Since my fan is not running I guess I can (for now) rule out the compressor as part of the problem? Correct?

I REALLY appreciate your help.


Another thing I noticed when looking at the fuse. The fuse no. 8 slot was empty, and from the pull-out card board map for the fuses I could see that fuse no. 8 was "motorsteuerung" To me that sound like "engine control" or something. Should I not have this fuse??

Prooobably a dumb question...

Thanks in advance!

xyzbird

In automatic recirculating air control (AUC mode), pollutant gasses are detected by the AUC sensor. Based on this input, the IHKA decides whether the system is to assume fresh air mode or recirculating air mode.