syoo8

I am having some HVAC issues (cold all the time except when the temperature **** is set all the way "high.")

I checked the thermistor under the driver's side headlamp, which gave me a 145 ohm (very low) resistance, independent of temperature. I will have to get a new one of those.

I decided to also check the setting motor, as described on page 87-113 of volume 4 of the WSM. Porsche gives you a nice picture of the setting motor in the WSM, but when I removed the driver's side panel of the center console, and looked "above my right calf" as Wally P suggested on his 12/9/2010 post, I could not find it.

Am I missing something?

Thank you all in advance.

syoo8

And here is a picture of what I see, versus what is on the WSM.

ammonman

You're in the right area but the setting motor is more toward the front of the car and a little higher up.

Mike

syoo8

Thanks for your reply Mike! Does this mean I have to disassemble more of the interior to get to it?

ammonman

I don't think so. Remember that the illustration from the WSM is as if you were looking directly toward the front of the car. You will be looking for a black box mounted to the side of the HVAC/Heater plenum with two plugs coming in from the rear of the car toward the front and a small arm connected to a linkage. The arm is between the setting motor and the plenum.

Mike

syoo8

Mike, thank you so much for your advice. All the best.

jcorenman

I think the shelf needs to come out to get to it.

Mrmerlin

I think you should replace the outside thermistor and leave the setting motor alone till this is done. Without the proper signal the setting motor wont function as it should,
they dont usually go bad either

syoo8

Thanks for your advice, Stan.

You are right: upon testing the setting motor, I got some weird results:

Plug 2
Terminal 3 to terminal 11: battery voltage (ok)
Terminal 4 to terminal 12: 3897 ohms (temp set to 65), 4854 ohms (temp set to 85) (ok)

Plug 1
Terminal 3 to ground: battery voltage (ok)
Terminal 8 to ground: .84v below battery voltage
Terminal 2 to ground: .84v below battery voltage
Terminal 9 to ground, temp set to 65: 0v (should be battery voltage)
Terminal 9 to ground, temp set to 85: 0v (voltage should be interrupted at 10%)
Terminal 10 to ground, vent open: 10.10v (should be 0v)
Terminal 10 to ground, vent closed: .84v below battery voltage
Terminal 1 to ground, vent open: 10.10v (should be 0v)
Terminal 1 to ground, vent closed: .84v below battery voltage

Could some of these results be attributable to something other than the bad thermistor?

Mrmerlin

you could remove the HVAC controller and open it looking for burned wire traces or the fried relay

Schocki

My temperature flap motor was bad last week and before you dig in any deeper, I would recommend you take it out and open it. Most of the time it is a bad solder spot on the electronics.
The housing has two halfs. In one sits the electronic unit, open, clean all contacts (especially those on the potentiometer) re-solder all electronic componentes.

Open the other side (small box) and clean the little movable contacts and their tracks.

Put it all back in and give it a try. Worked for me after 21 years of flawless serveice.

The problem is that as soon as it is on full hot it stays there AND the heater valve is ALL the time open. Because the arm that moves the flap also controlls the switch for the vacuum solenoid of the heater valve.

...and BTW this unit does not have a relay

Mrmerlin

sorry to be clear the HVAC relay is inside the control head and is used for running the A/C compressor system

syoo8

Thanks for your advice, Schocki. After cleaning and re-flowing the solder in the setting motor assembly, I got voltage in terminal 9 to ground, which is a better result than 0v previously.

I also pulled the HVAC control head and didn't see anything dirty or fried inside.

I reassembled everything and noticed that, like before, the linkage attached to the setting motor does not move. I am still getting some weird readings from terminal 1 to ground and terminal 10 to ground with the vent open.

Mrmerlin

check the fuses and the relays

Bill Ball

Four transistors inside the setting motor are known to go bad on occasion.

https://rennlist.com/forums/928-foru...w-working.html