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Jon Brush
01-22-1999, 11:20 PM
For those who don't check the E39 board, here is another take on the center vent cold air problem. I posted a request there asking Richard for help with how to access the motor:<p>"Jon, I had a same/similer problem in my 1990 535i. Have you checked the small motor between the obc and the glove<br>box. This motor should turn when you move the thumbwheel. In my case it was knocked out off the right position by<br>my stereo installer. It only needed to be rotated to the right angle and snaped back in. Hope this helps.<br>Richard"<br>

Glen Klym
01-23-1999, 01:24 PM
I just had this problem repaired at my local BMW dealer.<p>My problem went as follows:<br>Initial fault was a 'reversed' function of the thumbwheel (ie. Red=cold, Blue=hot).<p>This strange situation later was followed by cold air only.<p>Here's the deal:<br>The thumbwheel controls a motor that moves a mixing flap via a linkage.<br>The clamp connecting this linkage to the flap had broken off = flap stuck in a position delivering only cold outside air.<br>So, new clamp fixed that problem.<p>When the car is shut off the HVAC system sets flaps etc. to a default position.<br>By doing this the system 'knows' their position on startup.<br>There is a pin type stop that the motor/linkage comes to rest against in the defaul position.<br>On my car this stop has been broken off leading to the system mis-reading the default position.<br>Long-story-short this is why my thumbwheel usually operates in 'reverse', the motor is simply 'out-of-sync'.<br>The dealer told me that the only way to resolve this is to replace the 'heater-box' to the tune of $1000.<br>I'll learn to live with it<p>Cheers<br>Glen Klym<br>'89 E34 535i

Jon Brush
01-24-1999, 11:02 AM
The motor for the vent is under the dash,just as Richard said, accessed by following the instructions for R&R the microfilter (ie removing the glovebox, etc). Mine was NG, new one on order. The thumbwheel apparantly operates as a rheostat, controlling the vent flap electronically. I turned the flap manually so now I have heat from the dash vents. More when the new motor comes in and is replaced. <p>Cheers, <br>Jon Brush<p><i>: For those who don't check the E39 board, here is another take on the center vent cold air problem. I posted a request there asking Richard for help with how to access the motor:<p>: "Jon, I had a same/similer problem in my 1990 535i. Have you checked the small motor between the obc and the glove<br>: box. This motor should turn when you move the thumbwheel. In my case it was knocked out off the right position by<br>: my stereo installer. It only needed to be rotated to the right angle and snaped back in. Hope this helps.<br>: Richard"<p></i>


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