Guys (and gals), my dual zone AC started behaving strangely a couple weeks ago. Driver side is blowing cold but the passenger side is blowing warm ambient temperature air.

I tried turning off dual and turning back on, manuall setting both zones to same temperature, but the passenger side won't blow cold air.

Sometimes after driving for a few minutes, the passenger side starts blowing cooler air but not as cold as the driver side.

Does anybody know what could cause this problem?

Thanks in advance,
Dave

 

Sounds like a servo that operates a vent door is malfunctioning .

 

Agree with Blister, either blend door motor or stripped gears door or motor.

 

I had this same issue with my ES350. The guys said it might be the servo but on the 2007 model it does not have that. So I just recharged the freon and it worked. Usually when the freon runs low it goes to one side.

 

FREON is used to cool the coil and air is blown over it to supply cool air to the cabin. Low Freon would make the coil not get cold and all vents should suffer the same result. I never heard of this before.

 

I did not believe this will solve the problem at first but a couple of other guys on the ES350 side had the same issues. They recommend me to try this first and it worked

 

update.

thanks fellas, turns out it was the blend door motor issue. not as bad as i thought.

 

I have the same issue now, and just had it charged up 2 mo ago. I agree w the quote above. Unless there were two separate compressors and cores it wouldn't make sense that one side would cool andtand other wouldn't if coolant was low. There is another thread here where several people say this was the issue and adding more coolant solved the problem. So who can explain that?makes no sense to me, since it seems like all air is blowing in over the same set of cold and then being distributed through ducts. Right?

 

You are correct. That makes no sense that adding refrigerant solves that problem. The likelihood is that it is a blend door problem.

 

Even though it doesn't make sense to you, i would still try it. This is a problem on many cars, not just Lexus. If you do a search for "car a/c cold on one side", a lot of time the solution is adding refrigerant (R-134). Since you had to add refrigerant 2 months ago, you already know your system has a leak (Your car will not naturally leak coolant since it is a pressurized sealed system.

As for why it happens: I think it happens because the evaporator core is placed either more on the driver's side or passenger side in most cars. As the a/c blower blows air across the evaporator, the cool air takes the path of least resistance to escape. So whatever side the evaporator is on, ends up cold. Just my guess.

 

Someone explained in a similar thread that if refrigerant is low, it may cool just where it enters the coils, but not cool all the way through, and where it exits and is not cool, may be where it blows across on It's way to the drivers driver's side vents.

I had it charged for the first time since mfr 14 yrs ago and the show ran it on the computer and pressure tested for leaks before charging. So, though it seems you are right, a leak didn't show up on the diagnostic. I'll find out today though.