Testing interior temperature sensor

[Goosh]

1986 911 Turbo - I'm having problems with the auto-heating system and have read a bunch of the posts re auto-heat. My current question is: how do I test the interior temperature sensor - I know that I use a multi-meter, but what do parts of the sensor do I need to probe? Does the car need to be running or ignition on? The rear sensor in the left rear flapper seemed to test okay (I tested at the center console) - the ohm readings increased as the car cooled down - is this correct? Thanks in advance for your guidance

Goosh

[billybek]

Check this out, just thrashing this about today..
Heater is TOO hot

[cmonref]

Goosh,

Remove the interior sensor and look at the connection end. Your ohmmeter probes go on the very center contact and on the peripheral metal that serves as ground.

For the rear sensor at the flapper box, ohms will go up as it cools, and down as it heats up.

[Goosh]

Hi Bill & Brian - thanks for input - I have attached a photo of my interior sensor located behind the ash tray - I "assume" that I could take the resistance measurements off of the two wires coming out of either side of the sensor - is that okay? I got a reading of 2.12 ohms and it is probably 60 degrees in my garage - sure is cold here in California!
Thanks again for the help!

Goosh

[NE Ohio 911]

My autoheat did not work either. The ball socket that connects the unit to the lever came off. There is a small clip that tightens it up. The clip had snapped off so the socket would not stay attached to the unit. I made a new one out of wire to hold it on until my new one comes in from Pelican. You have probably already checked this but if you have not it could be your problem.

[Goosh]

Hi Doug - yep, already checked and mine had fallen off too - I also found that could not get the cable to move using the lever inside the center console (with the actuator arm removed) - so I have ordered a new cable and new cable guides to see if that will smooth the operation out. Thanks for the reply!

Goosh

[cmonref]

Goosh,

My instructions about measuring the resistance of the interior sensor assumed that the sensor was mounted between the visors -- I see that your car is not configured that way.

You ask if is OK to just put your probes on the two leads of the sensor -- I am not good at circuitry but am always leery of trying to measure things connected in a larger system because I do not know what alternate path may be affecting the measurement. Can't help with that question -- except to keep asking it until someone answers!

[aand]

Hi all, does anybody know if that little blower stays on all the time??

[Cloggie]

Originally Posted by aand

Hi all, does anybody know if that little blower stays on all the time??

Yes it runs all the time with ignition on run on my '89....