Hey y'all,

Question for you. Now that it's cold out, I've been using the heater, and noticing something odd. The air seems hotter than it's supposed to be at a given temperature. I set the knob to 60, and I get cold air. I set it to 61, and I get very, very hot air. Anywhere between 61-90 feels like the same air temperature. I haven't tried to measure temperature or anything, but it seems like I don't have much control of air temperature.

Is this common? Is it anything I can (or should) try to fix, or is it just that I'm expecting too much precision from a 13 year old automatic HVAC system?

Thanks!

 

Looks like the air-mix motor is getting tired and going out on you (most common). It is located below right center of dash, you need to slightly pull back the carpet to see it. Monitor the motion of the white plastic arm attached to the air mix motor as you adjust the temperature at the hvac control from hot to cold in small increments. Normally it should move in tiny steps as you adjust the temperature from cold to hot and vice versa.

If the air-mix arm stops moving after 61 or goes all way to the limiter then you may have a faulty motor or a hvac control unit (less common).
You can also remove the air mix motor while connected to the electrical harness and play with the temperature while monitoring the arm movement.
Although very unlikely on 2nd gen TL, it is also a good idea to check the control linkage and door for smooth movement by hand. The linkage and door is directly controlled by the air-mix motor, this test will isolate if the door is binding or not. Good luck.

 

Thank you sir! I went out today to fix it, and without me doing anything at all, the problem had resolved itself. So it's probably failing slowly, I'll keep an eye on it and decide if I want to do anything about it.

 

If it is the air-mix control, there is a no-cost fix that works nearly all the time. My son and I did this fix on my 2002 TL 3 years ago (when I bought the car we always got cold air and increasing the temp resulted in a "grinding" type of noise but no change in temp). Here are the general steps. I sure someone has photo-documented it as well.

• Remove the diverter control box from the heater box.
• On a clean towel, carefully unscrew and open the box.
• Note where all the gears reside.
• Examine the large gear for broken teeth. That where the motor cannot move the diverter door.
• Rotate the gear 180 degrees and reassemble and reinstall.

And Bob's your uncle.