92 SC400 Air Conditioning
 

Hi all,

I have a 92 Lexus SC400 that is having some air conditioning issues. When I turn on the AC, it'll blow for a few seconds, then the green light on the AC button will flash and it will stop working. If I push it again, it does the same exact thing. I recently had the relay replaced, so that isn't the problem. I'm trying to figure out the problem and the easiest way to fix it. I've looked on other posts here and it looks like it could be the Compressor's RPM sensor, or the compressor itself. Does anyone know the part number for the RPM sensor or if I buy a rebuilt/new compressor, is the RPM sensor part of the compressor? I've tried finding the sensor online, but have had no luck, so I thought I'd ask here and see if anyone has any ideas. Thank you!

The first thing to do is to run the A/C diagnostic program by holding down the PUSH-AUTO and Recirculate buttons simultaneously while your car is off and then turn your ignition key to ON but without starting. A series of electronic beeps will follow and then your A/C may display one or more A/C trouble codes on the HVAC screen. Write those numbers down. I believe A/C CEL 21 is for the ambient light sensor and that can be disregarded unless it is broad daylight outside.

What you describe could indeed be the compressor's revolution/RPM sensor or "lock sensor" however. I had this problem with an old SC300 A/C compressor a year ago and there were no trouble codes that specifically pinpointed the issue for me but the symptoms just based on observation and the age of the compressor gave me a hunch that the entire unit needed replacing. As it turned out I was right and replacing the compressor cured my A/C issue. The RPM/revolution/Lock sensor is technically available but realistically not worth replacing when you can get a new one with an entirely fresh compressor.

For the SC400's 1UZ-FE the Denso compressor part number is #471-1150. Denso's description says it has seals that will work with R12 or current R134a if you have not yet switched to the newer style refrigerant. It's available for about $320 brand new through Rockauto or Densoproducts. Whenever replacing the A/C compressor you should also replace the A/C receiver-drier at the same time which for the SC400 is Denso #478-2004.

Thank you!
 

Hi,
Thanks so much for your help. I just ordered a new compressor from Denso, and hopefully that'll fix the problem. I'll let you know.