Alright, Ive been working on this AC system for months and have exhausted the search function and my patience with this car.


Originally the AC wasn't working, self diagnostic test pulled code 00, compressor would kick on for about 10 seconds every time the car was started but never blow cold air.

Had an AC tech check it out, pressurize the system properly, didn't change anything at all.

Replaced the entire compressor set (expansion valve, etc…) and the AC still doesn't work, again it kicks on for the first 5-10 seconds when the car is started and this time it DOES blow cold but then shuts off. Self diagnostic code throws code 21 & 24 in both dark and full daylight.

Replaced the solar sensor today ($200) and the diagnostic code is gone (00), but nothing changed with the AC.

Pulled the low pressure switch and jumped it, again the compressor kicks on and then off after 10 seconds with the switch JUMPED!

Replaced the relay, no difference. Cleaned the air filter, no difference.

Can anyone suggest ANYTHING?! I really need to get this thing working, its only 105+ outside.

Thanks!

 

Wow, you covered a lot.

From a non expert ie me, have you tried resetting the ECU?

 

Any idea how to do that?

I unplugged the battery for 10+ minutes multiple times.

 

Honestly, no.

Im sure the guys in here can help.

Have you checked for a faulty wiring? Maybe ground issues?

 

Did you pressure test the system?

 

Yup had my ac mechanic test the whole system after he installed all of the new parts.

I checked the wiring to the best of my ability.

 

Just pulled all of the grounds and really cleaned them up, no help though

 

You might consider doing the pressure test yourself. Mechanics often lie. Just get some r134a from walmart with a pressure gauge. Connect to low pressure valve. Follow instructions and check pressure and frion level. It's possible that the mechanic didn't test at all or lied. If the system holds pressure, is fully charged, and compressor is spinning, that's really weird. There could also be a loose connection, but it sounds like you already checked. Is the AC light blinking??

 

Have you asked the dealer about a diagnosis . It might be worth an hour or so of labor to get to the bottom of the issue

 

As others have suggested, get the system pressure checked. You need to see both the high and low pressure readings. Many systems have cutouts for both. The gauges should tell the story. Hopefully the drier/filter was changed with everything else. Your new expansion valve could be clogged by junk in the lines so you're getting a high pressure cutout. Since you jumped the low pressure switch and it still cut out my bet is you have excessively high pressure.

 

The AC work is done by a guy I know who works out of his garage, was an AC tech forever and retired but still does it on his own for people he knows. Tests and charges my systems for free so I doubt he would be lying. He said he will take another look at it tomorrow for me.

I'll mention the expansion valve potentially being clogged tomorrow and yes the drier was replaced too.

AC light is not blinking.

 

Did you figure out the problem? My RX350 is having this same problem and Lexus delearship has replaced my compressor and condenser. This is beyond frustrating, as I am sure you well aware of this feeling!!

 

I have seen many times this being caused by a bad ambient temperature sensor. Also can be a bad board on the climate control panel. You need to also check the applicable relay or relays. I hate it when I see or hear shops that spend thousands without do a real diagnosis. I had someone show up at the shop after leaving the bmw dealership. They charged him over six thousand dollars replacing parts, and still no ac. He pulled in hooked it up . Ambient temperature sensor said minus 36 degrees Fahrenheit. Replaced the $15 sensor he had ac in his M5. The dealership ripped him off for thousands.

 

I agree it might be a high pressure issue. Unlike the old R12, you CAN put in too much R134. If it is too high, then the system will cutoff. There is an ambient temp/pressure chart somewhere on the internet you can refer too. Or you can just use common sense. When it is 90 degrees, don't fill up the system to the max, or else when it gets to 105 the pressure in the system will be too high.

Since it runs for 10 seconds, I would assume it is either a relay (which you checked) or a sensor reading. My guess is the 10 seconds the system runs put the pressure out over/under the limit somewhere.

Any chance you have access to Techstream?

 

On my 04 LS430 (very similar system) it was: 2 dead radiator fans!
Stumped a couple of good mechanics; they thought compressor, or blocked expansion valve.
I decided ATF that 1 fan had been dead for a long time; system could cool with just 1 fan; but when 2nd died, my symptoms were about like yours.
First thing I did: sprayed garden hose mist on condenser; things worked fine.
A set of fans with ECU on the big mounting frame that holds it all was $125 locally.
All is good now, and I have an extra ECU for the future.