Hi, I have a 2001 Lexus RX300. Recently the A/C light has started flashing randomly while using the A/C. Pressing the button re-enables it but it is a big pain.
The tried replacing the A/C relay with a Denso 574-0004 and to my surprise that did not fix the problem. The alternator was replaced around the time this started but could be coincidence.
I am not sure what else could be causing this and if there are any diagnostic modes on this model to help pinpoint the source and fix.
The A/C blows very cold when it is running so I think the charge is fine.
This happens whether in Auto mode or manual with recirculation on.
I would truly appreciate some help on the issue. Thanks.
I held the recirculate button and the auto ac button for 5 seconds and turned the key to on and I got a code 21 and a code 43 in the Temp field.

 

One of the common reason is belt slippage. Start by checking belt tension. I would advise that a proper gauge be used to set the tension.

If you happen to drive through some standing water [puddles included] the AC light might flash. Once things are dried out the flashing light gets fixed on its its own.

Salim

 

This thread on LexusOwnersClub might be helpful:
https://us.lexusownersclub.com/forum...iagnosis-help/

 

Hi Thanks for the quick reply, The belt is tight and there are no squeeks. The weather has been dry in AZ.
The Altenator with the larger tow package amps was recently replaced as well as the relay with a new Denso 567-0004.
It runs for a while then randomly starts blinking, pushing it reengages the A/C and I can feel a difference in the air temperature.
The temp is nice and cool when running. If the Freon and relay are good what else causes this behavior like a failing relay on a 2001 RX300?

 

I am not much of help when it gets to AC or even extreme mechanical issues.

Please see if there is a diagnostic mode for AC. There are simple interlocks that can cut out the AC when the refrigerant pressure is low. If you don't have the test equipment, a visit to AC shop might be worth it.

Salim

 

Seems correlated to the alternator being changed recently. Maybe the belt is too tight? That or the A/C compressor could be going out.

 

Talking about belt tension, there are two specs, one for new belt and another after 10 mins of use. If there are issues, please ensure the mechanic has the tension set per spec.

Salim

 

I held the recirculate button and the auto ac button for 5 seconds and turned the key to on and I got a code 21 and a code 43 in the Temp field.
Issue happened not long after replacing the altenator.
The A/C light randomly starts blinking and blowing warm air going down the road even after replacing the Denso relay with a new one. Note Denso looks to have replaced the relay with 567-0004 and does not reference replacement part numbers on their own part and site if that helps anyone out searching OEM..
What other diags do I need to run?
Where is the light sensor for code 21?
Does Code 21 or 43 cause the ac button to blink like this and turn off cooling?
The A/C light starts blinking at random intervals going down the road and starts blowing hot air. Pressing it twice off/on temporarily fixes the issue and it blows cold air until next time it flashes.
I cant correllate to ambient tempature, bumps, acceleration.

 

Do you have the 2 tension specs for the RX300 2001?

 

New: 150-185 lb-ft [less than 5 min run time]
Used: 95-135 lb-ft [more that 5min run time]

Salim

 

Would code 21 and 43 cause the AC light to start blinking like this and blow hot air randomly?

 

You would be better off by searching or contacting a professional. Help from me will be limited.

Search found this
https://www.clublexus.com/forums/per...de-43-fix.html

The other code is for solar/sun sensor. Mostlikely you are getting it is because the environment of test is with sun-light around. You can cover the sensor and see if it goes away.


Salim