rmk9785e Posted July 23, 2019 Share Posted July 23, 2019 On my 1999 RX300 AC, the 2 passenger side vents are delivering warmer air compared to the 2 vents on the driver side and 2 vents in the middle for the rear seats which provide cold air. Something is wrong with the airflow duct and control systems. Performed AC diagnostics but there is no error code. Can someone please point me to any documentation where I can find and trace the duct work? Quote Link to comment Share on other sites More sharing options...
Filehorse Posted July 23, 2019 Share Posted July 23, 2019 Most likely you have a problem with the Mode Servo which directs air flow to vents, defroster, heater, or mix. I replaced both the Mode Servo and the Air Mix Servo (which actually controls the temp of the air from the system). This is a common problem on this generation RX. The parts aren't particularly cheap but if you don't mind crawling under the dash both servos are a DIY type project. The following link has enough info to get your started and there are probably some videos on YouTube to help you out. Good luck. https://www.clublexus.com/forums/rx-1st-gen-1999-2003/281294-air-mix-servo.html Quote Link to comment Share on other sites More sharing options...
rmk9785e Posted August 5, 2020 Author Share Posted August 5, 2020 Thank you for the advice. I went through the exercise of removing the servos, cleaning and lubricating. I could have saved myself time and effort if I had first checked if they were performing as designed (which they were). 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. It is cooling very well. Quote Link to comment Share on other sites More sharing options...
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