Air Distribution Switch

[rasmuw]

The rotary control knob that directs the air to defrost, vents, and footwells in my M roadster has detents that are not at the 12-4-8 positions. One detent is at 6 o'clock, for example. The control also seems to prefer being turned clockwise. Prior to some console work I have planned for the next few days, are there adjustments or fixes for this? I'd rather have some ideas about how the control works before I begin.

[Blacklane]

There are several good threads listed in the Z3 FAQ sticky thread at the top of the forum page. Look under "Blend Door".

[rasmuw]

There are several good threads listed in the Z3 FAQ sticky thread at the top of the forum page. Look under "Blend Door".

Thanks, Blacklane, but those threads are about the (center) temperature control knob. My question is about the knob to its left.

[jfh]

Hi Rasmuw, I just did a fix on my center knob. Installed a ball link to fix a broken nub. The dials are connected and the detents are little bitty spring loaded things that click into grooves. I don't know how yours can be off the clock position but pull the radio, get a little mirror and see what's going on. IIRC, pull the radio, pull the knobs off the 3 dials and push. The the white plastic control piece will be more accessible.
Cheers, John

[rasmuw]

The dials are connected and the detents are little bitty spring loaded things that click into grooves. I don't know how yours can be off the clock position but pull the radio, get a little mirror and see what's going on. IIRC, pull the radio, pull the knobs off the 3 dials and push. The the white plastic control piece will be more accessible.
Cheers, John

Thanks, John. I pulled my radio today and pushed the control piece backwards. I haven't yet taken a good look at it since I got distracted removing the glove box to trace and remove the cable to the Alpine CD changer that was in the car when I bought it. (I'm installing a CD43.) I'll take a better look tomorrow.

I've attached a picture of my question--note the selector with the knob pointed to 6 o'clock.AM 1.JPG

[jfh]

The black knobs pull straight off. I had to wrap tape on the jaws of pliers to get one off, the others came off easier. Any chance the position knob is on wrong? I don't recall how the shaft is configured with the mechanism in back that holds the pins and moves the cable. I agree something is off somehow.

Good luck,

[cfmistry]

Thanks, Blacklane, but those threads are about the (center) temperature control knob. My question is about the knob to its left.

This is incorrect. The blend door issue affects the left knob (the blend knob); the one you are having problems with. Your issue is due to the foam around the blend door disintegrating and making it hard/impossible to turn the knob more than a certain amount. Do not try to overturn it as you will break the small plastic nub as mentioned above. Read about the blend door fix and your problem will be solved. This is not an issue with the knob itself. Good luck!

Cyrus

[Allan Parsons]

This is incorrect. The blend door issue affects the left knob (the blend knob); the one you are having problems with. Your issue is due to the foam around the blend door disintegrating and making it hard/impossible to turn the knob more than a certain amount. Do not try to overturn it as you will break the small plastic nub as mentioned above. Read about the blend door fix and your problem will be solved. This is not an issue with the knob itself. Good luck!

Cyrus

Odd,
The sticking blend door issue affects the center (temp) knob on my 01' roadster. I always assumed the blend door served as an air temp "mixer" and the left knob controlled a "diverter".

[cfmistry]

Odd,
The sticking blend door issue affects the center (temp) knob on my 01' roadster. I always assumed the blend door served as an air temp "mixer" and the left knob controlled a "diverter".

Maybe my mind is playing tricks on me! I'll look into it. Could be mistaken, I fixed it so long ago.

[BimmerBreaker]

Are they not all "blend doors" - either blending hot/cool air, or blending directionality of vents - center/feet?

Either way, the problem is not the knob itself... take the center console out and take a peek behind. The issue should be pretty obvious once you have it apart and are turning the knob with the backside of the unit exposed.

[rasmuw]

I'd intended to take a closer look at the heater control issue back in November but work got in the way until the last two weeks. Today I took a close look at the back of the heater control panel. There are three levers with their nubs in two cam wheels. The bottom of the levers are each attached to a Bowden cable. The two cam wheels have shafts which project through the control panel to which the knobs attach. (The third knob controls the fan switch.) The back of the panel is shown in the first picture. Note that the white lever, which is sandwiched between the red and green, is the one that frequently has a broken nub due to the blend door issue mentioned in several threads. It is able to work independently of the red and green levers, controlled by what I referred to in my initial post as the air distribution switch. The red and green levers must work together since their nubs sit in the left cam wheel. The green lever controls the flaps to the floor. The red lever might control the defroster/dash vent flaps--I hear things moving but I couldn't see them.

The nub on the white lever was repaired by the most recent previous owner with a metal hobby store knob, referenced in the blend door threads. The problem I have is the positioning of the air distribution control. That control only liked to move clockwise, and I've found the reason--see the second picture. Cams are found on the front and back of this piece. The side shown is the front, into which the nub of the green lever sits. When turned clockwise, the nub wants to stay to the outside of the cam. Turned counter-clockwise, the nub follows the inside of the track, so to speak, and gets caught in the void to the inside of the broken track.

The cam is not available separately, of course, and I don't care to spend $90+ to get a whole used assembly. I am going to try to fill the track with Silly Putty and fill the void with Plast-Aid. If it doesn't work well, I'll buy an assembly and remove the cam wheel. Diagram of Heater Controls Rear.jpgHeater Cam.JPG

[Dakar Ole]

You could maybe try putting a piece of paper in the void and rub with a pencil to get the shape for a piece of brass shim. Then cut the shim and crazy glue it in and reinforce behind with epoxy. Just thinking out loud.

[rasmuw]

Thanks. I thought about the brass but decided it would be difficult to get the seam with the broken track tight enough. The Plast-Aid would make a seamless transition, but the challenge is getting the Silly Putty to form correctly. I came close, and the action of the mechanism works well enough now. Heater Cam After.JPG

I'm still not sure why I had a detent with this knob at the 6 o'clock position, which was the reason for my initial post. I know that after working the Bowden cables back and forth that the system works more easily. I should not have gotten any detents at all, since part of the assembly that creates those "stops" is missing. That part is shown at the top right of the first picture in post #11. The little springy nub on that part (missing in my case) clicks into place at the three depressions on the edge of the cam.

[rasmuw]

I decided to buy a used heater control panel and found one that was inexpensive even shipped from England. Better yet, it was in perfect condition. From it, I took the air distribution cam that I had tried to repair (but was still a little rough when turning counterclockwise) and the "spring nub" that clicks into the detents of the left air distribution knob. The blend door needed no adjustment with the center control making the blend door shut with a thunk just as the knob is turned to full cold. I wish I'd bought the panel earlier as it would have saved me from purchasing a new backlit face panel. My original was cracked. I'm happy to have a smooth, functional panel!

If anyone needs any replacement pieces for their own heater control, feel free to contact me.