I have a 94 LS400 with 104,000mi. About 2 months after have the timing belt and water-pump replaced, I started having a loud grinding noise from the front of the engine. At first I though it was a problem with the replacement of the timing belt, but after a few miles, the A/C control unit on the dash went completely dark, all the lights went out, and the unit wouldn't work. I then attributed the noise to the A/C compressor. I took it to a local mechanic (not Lexus dealer), who replaced the compressor (said it was bad) and replaced the fuse to the A/C unit in the dash, but he is unable to get the A/C to come back on. He is telling me that the electronic control unit in the dash is bad and needs to be replaced for $900.

Any ideas as to what he may have missed at this point. Any other fuses or switches to get the unit to function? I appreciate any help I can get at this time. I've decided to go without any heat/cooling so far but it's going to get cold pretty soon.

 

A tricky moment in the replacement of an A/C compressor is the "locked rotor sensor" at the rear of the compressor. Although replacement compressors may have a sensor in that location, it is nt guaranteed to work. As a general rule, you should swap your sensor out of the bad compressor and install it in the new one.

A loud grinding sound should not be allowed to run amok for "a few miles".

It is possible that if you have lost power to the climate control head. A thorough diagnosis using the factory-specified order of inquiry will help you narrow down the culprit.

Electrical supply to the A/C control unit goes through the dome fuse and main fusible link, and there are two big connectors on the way to the control head. There is a indicator lamp test you can do by pressing the "AUTO" and "REC" buttons when you turn on the ignition. All indicator lamps should go on for one second four times. Then you will get any diagnostic codes on the display.
Colin

 

Edit. Whoops not apllicable to your problem but I will leave the info for those that do need a new compressor:

Look for Denso 471-1219 on Ebay. I think you will be pleasantly surprised!

Use BG FrigiQuiet II. It is great for increasing your compressors lifespan.