Hi guys! I have a 2001 Lexus LS 430 UL and my A/C is having weird problems. When the engine's RPM is low, the A/C compressor would disengage and the A/C button would blink. But pressing the button twice would restart the compressor, blowing cold air as if nothing was wrong with it. When the RPM is high, the A/C works as it should. My OBD scanner showed no error codes and the A/C self diagnostic program also showed no current error codes. What could be the problem?

 

It could be a low charge of refrigerant. The compressor disengages if it doesn't see enough high side pressure. At higher rpm it's able to keep the pressure up. It could also be high pressure switch out of tolerance or problem with the orifice tube.

 

Thanks for your reply! Actually I had a mechanic check the A/C system and he did not find anything wrong with the system. There is no leak and he recharged the system with the adequate amount. The pressure switch was replaced 3 months ago so it is not likely to fail. I will check the orifice tube to see if there is any problem.

 

Hope it's not the compressor.

 

Just a quick update on the issue. When I set the temperature to over 68 degrees, all the problems go away and my A/C blows cold air even when the RPM is low. Any thoughts on why?

 

Last update on the issue, I replaced the A/C compressor magnetic clutch relay with a new one I bought from Autozone and the problem goes away. The new relay's name is Duralast relay #20382 and I wonder if anyone has used such relay on their LS 430. Would it be okay for me to use it?

 

Should be fine.

 

I recharged the system yesterday and now the A/C is malfunctioning again! What could be wrong here? Expansion valve?

 

Do you have a trusty worthy Independent mechanic or A/C shop to diagnose it for you or you could go to the dealer and for a one time diagnostic fee (usually $100 and change) they should point you in the right direction. You don't want to throw parts at an old car to try to find out what's wrong. Good luck and let us know how you make out. PS....Not too much on this forum with A/C issues for the LS430.

 

Bocatrip, thank you for your advice! I will go to an A/C shop to have my car diagnosed.

 

By the way, I noticed a pool of water underneath my car after I left my car parked for 4 hours. Is it possible that my A/C system is frozen up, causing the compressor to stop?

 

When you recharged the system did you just add gas or did you recover the existing gas in the system and evacuate then recharge with new gas?

If the A/C is running you will get water from condensation on the evaporator coil draining out under the car. If your evaporator coil is frozen you will notice reduced airflow from the system.

 

I just added some gas to fill the system up. Also, the reason why I filled the system up is that I thought my A/C problem was not related to the level of refrigerant, so filling it up should not affect anything, turns out I am wrong. I actually reduced the amount of refrigerant on purpose when I replaced the relay, because I saw from another website that someone solved their A/C problem when they took some refrigerant out. Up to now, I still have not figured out why replacing the relay and taking some refrigerant out of the system would work, but it did work.

 

I would have a shop hook up their gauges to your car and check system pressures. Having too much refrigerant will cause issues, just as having low charge will. Also if you used an off the shelf refrigerant that also had oil or leak stop in it I would be weary of issues down the road.

 

I took the car to both my mechanic and local dealer lately and got different results. The mechanic made sure that the system had no leak and every component of the system, like A/C compressor and evaporator, was replaced around a year ago, but they could not find the reason why the compressor keeps kicking off. The dealer said it was the compressor but they were not sure if it was the root problem. Currently the system works fine but I discovered that when the engine's RPM drops below 600, the compressor would kick off. Now I am considering if there is a way to keep the RPM above 600 so to make the system work.