welsch1505

Two years ago we had both leaking A/C radiator coils replaced. Since that time we have noticed that on a hot day (above 84 degrees) the clutch doesn't hold energized when the A/C button is pressed and released. The button's light begins to flash. Hitting it again might result in proper operation or it might fail again. There is no computer error code registered. Reving the engine and hitting the button usually allows the light and clutch to hold properly. Other forum answers suggest replacement of the clutch relay which we have done to no avail. The coolant pressures have been checked numerous times. Once the clutch energizes the problem will not occur ( even for long trips) until the car is parked and turned off for more than 15 minutes. The car performs well in all other respects and is regularly serviced. It has an odometer reading of over 200K. The local Lexus dealer is baffled as are all the " auto experts" I have spoken to. Any new thoughts or suggestions?

mmarshall

Welcome to CL as a new poster.

Has the A/C button itself been replaced or inspected? After 200K miles and 16 years of turning it on and off, the button's electrical contacts may be excessively worn. That wouldn't necessarily account for the engine-rev holding, but it would probably be a good place to start.

Also, the 15-minute period you mention, after turning the engine off, produces a period of "heat soak" under the hood where underhood temperatures rapidly spike and then do a cool-down (the rate of cooldownat least partly dependent on the outside temperature), which causes the clutch parts to expand and contract, possibly affecting how they engage. With a lot of wear on the clutch itself, that could be at least part of the problem.

BTW, we also have two other possible CL forums for questions like this.

https://www.clublexus.com/forums/gs-models-4/

https://www.clublexus.com/forums/maintenance-11/

blacksc400

iTrader: (4)

Welcome to CL. And moved to correct forum

Hope you fix your problem soon.

monkey92

iTrader: (3)

im having a similar problem on my 98 gs300 as well. my AC will turn off when i first turn on the car during the day and when i go on reverse sometimes. hopefully someone who has had this problem and figured out what the problem is can chime in.

welsch1505

Thank you MMARSHAL, This problem only became apparent after the radiator coils were changed. Since reving the engine clears the problem I became suspicious of the alternator possibly not giving full voltage in idle. In checking that, I read 14.12 volts "solid"at idle and also with higher engine speed. Looks good! When I depress the A/C button it reads 14.11 as the compressor adds drag. Also looks OK.... We find that in every case, the problem clears when the car begins to accelerate. The temperature has to be above 84 degrees for it to "most often" fail. The A/C switch itself, always functions fine at lower temps. I think this is one for the design engineers!

welsch1505

MMARSHAL, Just a quick memo. It just occurred to me that the A/C computer WAS replaced along with the clutch relay, so your thought of replacing the switch has already been done. It sure looks like a compressor clutch issue but I don't see replacing that with such a minor intermittent.