I have a 2009 LS460 with 119k on the clock. Last winter noticed the AC system began this thing where after parked for over an hour or so, the temp reset to 75, and the other settings went to some neutral setting. So when this condition occurs (practically every time I get in the car) I have to wait for about a minute before I get anything from the AC or heat system, and it all has to be reset.

When I first bought the car (2 yrs ago, used, 70k on the clock) this condition was not present.

Recently, I noticed that unless the car is moving, I get only outside temp air, regardless of the settings in cold temperatures where I need heat, defrost, etc..

Ideas?

Thanks in advance.

 

This has been discussed on several threads. Have you searched? Bottom line is first verify your coolant level is where it needs to be. Coolant top off to appropriate level resolved it for most of us who had the issue you mentioned Sent from my iPhone using IB AutoGroup

 

I had this same issue. It can be caused by breaking the blend door on the cabin air filter housing when attempting to change the filter. If you changed the cabin air filter and were not careful to follow the proper procedure, you can foul things up.

However, this problem can also occur if the wiring harness connected to the climate system develops a short, which is what happened in my car. The blend door worked fine, and I had not attempted to change the filter when the problem arose, so I knew it wasn't that issue. The car was covered by extended warranty, so I had the dealer go hunting the issue. They determined one of the boards in the climate system was toast. They replaced the board, and then noticed that the harness was shorting it out. So they replaced the harness too. No problem since.

Fortunately it was covered under the extended warranty. Otherwise it's something like $900 to fix. Which is actually cheaper than some of the other things that can go wrong with servos and such that can also cause the 75 degree behavior.

So there are a few things that can cause the climate system to reset, and if it isn't your blend door, you probably need to get a mechanic to look into it.

The heater issue was already covered by CJITTY, so you'll want to check the coolant level.

Good luck!

Chuck

 

Many thanks for the information - dealer changed the air filter and my temp was messed up, reset as per the forum
Great forum