Last night I found something strange, that may be related to the random engine shutoff. (2004 TL)

It was cold last night and I was driving with a passenger. I had been driving for a good 30 minutes so the engine was fully warm. I turned on the a/c (dual off) and put it on 80 degrees. Both sides said 80, but the passenger side was blowing out cold air. Like it was stuck on "Lo" temp, even while the display said 80.

What could be causing this?

By the way, Ive had this car for over a year, and have had no problems with it until now. It just seems like everything is happening at once.

 

I have a similar problem with my 04 TL. If i want heat I have to turn it all the way up and it will get warm, for cold all they way down nothing in between. Any suggestions would be helpful.

 

I had the same problem in my TL before I sold it .. weird.

 

Usually when we see this at work, it's due to a faulty air mix motor. Doesn't happen often, but this is usually the case. I know a lot of people hate the dealership, but our HDS is very helpful in diagnosing the problem. If the motor is faulty, it'll ususally set a body DTC, which of course the HDS can read. Also, the HDS can perform a climate control unit test, to also aid in diag. If that's the case, then it's on to the trouble shooting, which isn't that hard for this particular motor. Hope this helps!

 

I literally just got it back from the dealership, and they said it didnt throw any codes. Would anything else cause this problem other than the motor that would throw a code?

 

Well, like I said, it won't always throw a code. If it were me, my next thing would be to either a) manually watch to see if the passenger air mix door is moving when commanded to, and/or troubleshoot the passenger air mix motor according to the manual. This would included manually powering it to open/shut, as well as checking for any opens between the climate control unit and the motor itself. While in there, checking for binding or disconnected rods, etc would be a good thing to do too.

I had one TSX that had a plugged heater core due to improper coolant, but this caused a heat loss on the driver's side, seeing that the coolant lines to the core come in the passenger side...

 

Switch it back and forth from different vent settings to see if perhaps you have a stuck vent. This happened once to me with a floor vent in the winter. It got stuck on outside air so it was not cycling air across the heater coil. I cycled the vents several times from floor to dash defrost (none of which was I using the A/C) and it freed itself up. I has never happened since.