I drive a 2004 TL and just started having this issue when the weather turned cold. Sometimes when I get in the car and am using just the vent, I will kick the temp to 68 or something comfortable. Used to, the temp would come up to that level as the car warmed up.

Now, it will stay at the coldest setting (intermittantly) until I run it all the way up to high, on both sides, and then when I bring it back down, it's okay.

Took it in for that and another issue, and after the service advisor got it through his head (although he seemed very doubtful) they checked out the entire AC and Heat system, and of course, everything checked out fine.

Has anyone run into this? Is something getting stuck? I'd say it does it 50% of the time when I crank the car and it's already set to LO. It's just a nuisance, but nuisances get OLD!

Thanks.

 

I have the exact problem as you. The only way to get the heat up is turn temp up to Hi Mode and then lower temp back down with the AC set to Off. This has been going on for a while. In between this problem, I had the AC completely shutdown during the summer and gotten a new transistor replaced ($200 at dealer).

The problem is very annoying and has not been pinpointed.