Hello all,

I've had problems with my '99 RX300 before, but have always been able to find people with similar symptoms online and so have never had to post. This one's new, as far as I can tell: the a/c blows cold on the driver's side but room temperature (at least) on the passenger's side. In fact, if I close the passenger-side window vent and put my hand over the passenger-side dash vent, I can actually feel the otherwise cold air coming out of the driver's side vents get a bit warmer, as if the hot air from the passenger's side needs to get out somewhere.

This wouldn't confuse me on a car with dual-zone a/c, but I can't figure it out in our Lexus. Any ideas? I'd rather get some input from the disinterested experts here before I throw myself at the mercy of my dealer.

Many thanks,

--Chris

 

Common problem. Somrtimes you can fix it by just disconnecting the negative battery terminal for a few minutes to reset everything. If that doesn't do it you will need to clean air mix servo. Do a search on this forum for "servo" for lots of info.

 

I would try this too, probably just a glitch in the climate control system.

 

We had the same problem a month ago on my '99 RX. They thought it was a balky (I forget what he called it) "fan motor" , but in the end the freon just ran out. They checked for leaks and there were none. However, the AC was never repaired and it is 9.75 years old. It works great now.

 

This sounds like your air mix servo is hanging up. Do a search on "air mix servo" on this forum and you'll find the following link among others:

https://www.clublexus.com/forums/sho...d.php?t=281294

 

Thanks to all for the suggestions - I guess these pieces "only" last about 10 years. I followed the instructions to remove, clean and reinstall the servo closest to the passenger seat, which was the only one I could reach. Unfortunately, that doesn't seem to have been the problem. Next step is adding freon, and asking for tips on the "Air mix servo" thread. Thanks to all for pointing me in the right direction.

 

For some reason, this link doesn't work. Granted that it is almost 11 years old, Do links and images from older posts 'age out'?

 

Well, there are two servos there and usually, it's the harder one to get to that goes out.

 

I had this problem as well. The cause was low Freon. The RX300 does not control the air flow separately twixt Driver/Pass sides. It is simply that the left side of the evap feeds the left (driver's side) and right feeds the passenger.
Top of the Freon using the site glass if it has been a few years. I had this problem a few years back and like others I thought there was a control problem. I spent a lot of time inspecting with temp sensor and usb cameras only to have a duh slap the forehead moment.
EXPLANATION: The evaporator feed (in and out) is on the top left corner as the driver sits. When Freon is low only the top left gets cold.
I topped mine off a couple more times returning the system to excellent cooling but eventually I had to replace the leaking evaporator. See my post on replacing the evap without tearing the dash apart. BTW my AC is still working fine. Have not had to look at it since the evap replacement.
Good luck. BTW I was ticked at myself that I had not checked the Freon first. My sight glass was foam prior to top off.

 

Thank you. I took the car to a shop. They diagnosed and advised me it was low on Freon (0.5 lb), vacuum tested, replaced 2 valves and refilled gas to 1.3 lb with PAG Oil w/Fluorescent Dye. They could not find the leak.
They charged me the following:
R134 Freon $29.99
321 A/C Vavles (2) $20.00
JB Pag Oil $19.99
Plus labor and tax.

It is cooling very well.

 

Before we took it to the shop and had the above work done, it cooled only the driver side so we were glad with coolant being topped off, it was fully cooling on all outlets. Didn't have to use the cooling function during winter.
Well, summer has just started and our air conditioner doesn't work anymore at all other than throwing warm air. Is it possible that the gas leaked during winter?
Where do we start troubleshooting?.

 

Last August I took the car to a shop because there was no cool air from the passenger side vents. They diagnosed it to be low on Freon, vacuum tested it, replaced 2 valves and refilled Freon to 1.3 lb with PAG Oil w/Fluorescent Dye. They could not find the leak.

They charged me the following:

R134 Freon $29.99

321 A/C Valves (2) $20.00

JB Pag Oil $19.99

Plus labor and tax.

It was cooling very well but then I didn't have to use the cooling function during winter.

Well, weather is getting hot and our air conditioner doesn't work anymore at all other than throwing warm air. Is it possible that all the gas leaked during winter?

Where do we start troubleshooting?

 

Most shops offer 1 year part & labor warranty. I would suggest that take it back to them.

Since they added dye ... a small leak takes time to leave a trace, so you may find the real source this time.

Salim
ps: One must run the AC even in winter times [once a month at min] to lube the internal seals.