Climate Control Fan Runs With Ignition Off

[1983sc]

I have a 2002 X5 4.4i with automatic climate control. Recently I have discovered that after shutting the car off, sometimes the heater fan begins to cycle on and off on it own. It cycles to a high fan speed, easily heard outside the car. Once it caused a dead battery after 3 hours and the second time I caught it before the battery went dead. If I shut the AC/heater fan and control off (reduce fan speed to lowest level and push the fan contol again until the display shuts off) before I shut the engine off, I don't experience the problem. Has anyone encountered this problem? I would assume the ignition switch cuts power to the AC/heater module and fan, like other accessories - e.g. the radio, instrument cluster and heater control display. But that doesn't seem to be the case with my car. Has anyone else seen this problem? Does anyone know the fix for it? I've not been to the dealer yet for fear they will just throw parts at it and hope for the best.

[The Cleaner]

I hear my engine fan after shut down, not the Interior fan.

[vinuneuro]

this sounds like a final stage resistor symptom as well

[1983sc]

Thanks for your reply. The sound I hear is air going into the grill at the back of the hood. I can also feel the air coming out of the ducts inside the car.

[Quicksilver]

BMW has an option where if you set a timer it will run the vent system for a determined time. Perhaps you somehow set that timer and it's just doing it's job. Check your manual. It will spell out how to enable/disable that option. For example on page 116 of the 2005 manual it states:

116n
Independent ventilation*
You can use this system to ventilate the
interior and lower its temperature, using
the blower of the independent ventilation
or of the automatic climate control.
The independent ventilation is operated
via the MID Multi-Information Display,
refer to page 87, or via the onboard
computer, refer to the separate
Owner's Manual.
You can set two different times for the
system to start; it will remain active for
30 minutes. You can also switch it on
and off directly. Since the system uses
a substantial amount of electrical current,
you should refrain from switching
it on twice in succession without allowing
the battery to be recharged in normal
operation between use.
When a preselected activation time is
set, the independent ventilation is operational
at outside temperatures above
approx. 607/166, or by direct switch
activation.
The air enters the passenger compartment
through the vent outlets in the
instrument cluster, which can be
adjusted for both direction and airflow.
Therefore, the vent outlets must be
open for the system to operate.

[1983sc]

Quicksilver, Thanks very much for the lead! I'll check my Owners Manual and give feedback if it solves the problem.

[1983sc]

I looked at my manual and the Independent ventilation system is discribed witha reference to page 83 for control with the MID. I checked the MID and found that there were no preset times (2 possible) entered for this function. It is possible to turn it on manually as well, I did that a couple times to see what happens and it is acts similar to what I have observed. Since it would take 2 independent "miss-hits" of the control panel with the key in the "1" position (versus 2 - run or 0 - Off) to turn the fan on, it is unlikely that I did it twice within a few days - but not impossible. I'll keep an eye on it and if it happens again I'll start looking for that final stage resistor Vinuneuro mentioned. Where is it anywat?

Thanks again to all for the feedback!

[elric75]

Almost certainly final stage resistor. My 2000 had this, and eventually it got bad enough to kill the battery.

[TitanSilber3.0]

Anybody have any idea if the final stage resistor would also cause erratic fan behavior in a manual climate control version?

The fan has a mind of it's own these days and seems to pulse high/low/high/low in one second intervals.

[Zulu95]

Originally Posted by TitanSilber3.0

Anybody have any idea if the final stage resistor would also cause erratic fan behavior in a manual climate control version?

The fan has a mind of it's own these days and seems to pulse high/low/high/low in one second intervals.

FSR sounds like a good place to start. They only cost $70 on Ebay.