Heater Control Valve question

[fignewton]

I’ve looked through the archives and have another question that isn’t quite covered. Today, it was warm enough that I didn’t need any heat, so I turned the control valve back toward the cool side. I noted that when I got it vertical between cool/heat, I met resistance. It did not want to easily turn farther counterclockwise. I gently worked it back and forth until it went “click” like there is a switch/step at that point, and then it turned smoothly all the way to cool. I then got ambient air through the system. I have gone back out a couple of times and played with it, and each time I get to the same point (just after dead vertical) I get the same effect. I can hear something moving behind the panel, but I’m not hearing a clunk like I saw referenced in the archives when going to cool and the door flap closes.
Since I have no other reference car, can folks tell me if this sounds normal, or if I prob have something going on in the cable/linkage/arms. At no time does anything bind, other than crossing that “step” at the same point either direction. I have not been back out in the car to see if I can cycle from cool to warm effectively, as it’s pouring down rain here. Thought I’d check before breaking something.
Thanks

[Muzz258]

Hi

Your symptoms sound like the control I had before the pin broke on the heat control knob. The air blend flap is sticking, which is the step you need to get over.

Check this by taking out the kick panels from the right hand side and adjust the bowden cable at the air flap end. I put a zip tie around the end of the cable in the gap that is created. See If this removes the stepping point.

[2002Z3]

My 2002 has a sticky flap "vane" too. The old semi-rubber gasket is degraded and sticks to the vent housing. I just leave the temp knob at about 1 PM to keep the flap from seating against the lip of the housing. I need to get in there and sort this out. I did take apart the glove compartment about 5 or so years ago and adjusted the cable to "help" get more leverage, but sticky old foam is what it is. A simple fix, but a pain to implement. It only matter to me now since I live in Washington. I was in So CA before and never used the heater. Uh... I need it here. I only get decent heat on fan #3. Fully purged. Even with this little bug, I still love my Z3. Best car I have ever owned. If she were human, I would marry her. Reliable, fast, sexy, treats me nicely and only bites a little. Ooops. TMI! ;D

[Tallyho322]

My 2002 has a sticky flap "vane" too. The old semi-rubber gasket is degraded and sticks to the vent housing. I just leave the temp knob at about 1 PM to keep the flap from seating against the lip of the housing. I need to get in there and sort this out. I did take apart the glove compartment about 5 or so years ago and adjusted the cable to "help" get more leverage, but sticky old foam is what it is. A simple fix, but a pain to implement. It only matter to me now since I live in Washington. I was in So CA before and never used the heater. Uh... I need it here. I only get decent heat on fan #3. Fully purged. Even with this little bug, I still love my Z3. Best car I have ever owned. If she were human, I would marry her. Reliable, fast, sexy, treats me nicely and only bites a little. Ooops. TMI! ;D

I tried to baby mine too... until the little pin finally broke off control knob. Used the ball stud trick learned here to fix it.

Greg

[fignewton]

Update. Pulled the glove box assy yesterday to get a better look at the cable adjustment. All is good there, and the blend door moves easily both directions--once you get past the little "step" between hot and cold. It feels like it's in the control itself. I wonder if it may be the microswitch to open the heater control once you go to the hot side that I'm feeling. Nothing seems to be binding or in distress. I just have to be gentle with switching it past that point. Guess time will tell...

[me77]

The heater control switch gets activated as soon as you move the dial a little bit from totally cold/blue.

[fignewton]

The heater control switch gets activated as soon as you move the dial a little bit from totally cold/blue.

So the switch activates just after moving from full cool on the blue side? I haven’t found a good description of how the heater control valve works to change the flow into the heater core. Does the microswitch control this like a rheostat? The center control knob sees to only work the blend door from what I can tell, so what controls the water control valve to the heater core? Is it either all open/closed, with the blend door affecting the air mix for temp variability? Or does the flow vary through the core? (Like on other cars I’ve had with a manual cable controlling the water valve.)
Still not sure what is causing my notchy place at straight up and down. Unless it’s the nib hanging on something or getting ready to break. May have to pull it apart to be sure.
Thanks all!

[magnetchief]

The micro switch just opens the valves to allow hot coolant to flow to the heater matrix.

The notch you mention is very typical.
It’s caused by the blend flap insulating foam breaking down / causing a restriction.

It’s repairable. But a bitch.

Most people just turn the control till it sticks, then apply slight pressure till it pops open.

Don’t force it or the control dial could break.


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[Tfehd]

Under the hood.. the heater control valve wire runs from the valve over against the fire wall and then down in behind the steering column. I can see the other end of the plug.. unplugged for some reason.. But I cannot figure out where it should be plugged into.

Help appreciated