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Old 08-28-2011, 10:53 PM   #1
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Join Date: May 2011
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E46 M3 Climate Control IHKA AC HVAC wont turn on

Thought I would drop this info for those out there looking for it. I searched and didn't find what I needed.


The older 10 style climate control unit in my 01 M3 took a crap.


Went out to use the car mid-day, and the HVAC unit would not turn on. Meaning that it did not automatically start up and begin cooling / heating to the last setting (normal). Also, manually it would not respond to any buttons pressed on the unit. I drove with no air.

Next time I turned on the car, the climate control unit worked. Thought it was fluke, and forgot about it.

A week later, while driving the HVAC unit cycled on and off randomly and frequently. Got home turned car off. Unit never came back on.

Further investigating:

The unit would not respond when pressing any buttons.

Turning on the interior lights, all of the correct lights lit up on the unit.

I took the unit out and all connectors were tight. disconnected the largest one (it has a sliding latch) and the blower turned on and hot air came out vents.

Disconnected the battery, let sit for 60+ seconds, reconnected and nothing.

Thought process:

From what I have read, when the FSR resistor goes, you loose fan control. However, all other functions are normal. In my case, when the unit worked I had full control of fan with no issues.

Took the Climate control unit out and replaced it with a used one today and it corrected the issue. Bought it for 50 dollars from a guy on Craigslist.

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Old 08-28-2011, 11:46 PM   #2
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I have had the same problem happen to me 3 times so far this summer. I was going to make a similar thread seeing if anyone knew what was the issue. Hopefully someone here knows... I don't know if it is worth fixing (yet) seeing as it only happens about 1 out of 100 times I turn on my car.
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Old 08-30-2011, 01:51 PM   #3
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Its the actual unit, they fail, some faster than others. I would just be prepared for the day it just no longer turns on.

Does anyone know how to repair these units? I know that the E36 has a resistor that can be replaced. I found no such luck for the E46. Is there a repair shop online that does these repairs?

As for now it seems you just replace the whole thing.
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Old 06-11-2013, 06:07 AM   #4
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Hi Pheonix,

I'm having the same problem the unit will not start at all until i disconnect it from the cable or just pull fuse 28,62,63 out and in.
Sometimes the Unit stays on all the time even after motor off and keys out.
Did you have more problems after replacing the HVAC unit?
I even replaced the FSR but still having problems although battery drain is not an issue any more.

Last edited by Phonix6; 06-11-2013 at 06:11 AM. Reason: Update
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Old 06-12-2013, 03:43 PM   #5
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My Ride: 2005 BMW M3 6MT Vert
E46 M3 Climate Control IHKA AC HVAC wont turn on

I had the same exact problem in my 330ci. Sometimes after I turned the car off the HVAC unit would stay lit up and the blower would run. If I pulled the fuse and put it back in things would return to normal. On a couple of occasions it would just die completely while driving. No lights or response from the buttons. I even replaced the HVAC and the problems still surfaced. I read some where that the FSR will cause this. I since traded up to an M3 so I never got to change the resistor. I do however still have the other HVAC unit. It the new style from an 05 M3 is any of you are interested in it. PM me.

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Old 06-12-2013, 04:14 PM   #6
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mine failed too causing the water valve to drain battery and no heat.

easy to replace but hard to confirm it's the control panel. $50 for a used one for me solved the problem.
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Old 06-13-2013, 06:58 AM   #7
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Just a follow up. Two weeks ago, my AC went out again. However this time it was the Final Stage Resistor (FSR).

Climate Control Unit operated normally, however, I had no blower control. If i put my hand against the vent air was barely coming out, more at high speed. The CCU responded when I increased the blower fan speed, but the fan did not.

This happened during a heat wave. It was down for three days, then on my way to my mechanic it started working again.

I had the fsr replaced any how.

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