Replaced a dead battery. A/C was working on the way to the store (I replaced battery in store parking lot). A/C has not worked since. At the dash, the system appears to be operating normally IE: no flashing green switch lights..... it's just blowing ambient temp air. No sign of leaks or oil on components that are visible. I don't have a pressure gauge but I did tap the high pressure valve and nearly got my head blown off (was wearing safety glasses). I can see fluid and the odd bubble in the sight glass. The engine RPM clearly increase and decreases as the A/c is turned on and off. I ran the A/C self-diagnostic feature and got '00' (Normal). Anyone have any idea what might be causing my problem? 2005 LS430 Ultra Premium (Canadian) with 29150 miles on the clock. Thanks

 

Strangely coincidental that it stopped blowing cold air immediately after a battery change. Several ECUs are supposed to be re-initializated after losing power, but I didn't think AC was one of those systems.

Something you can try - with the car on, try changing temperature from coldest to warmest, and back, and cycle through the various fan servomotor options. Try to listen for the blend doors/motors moving as they should. Window/sunroof/seat ECUs are initialized by moving all the way one way, then all the way back, once or twice.

Check fuses/electrical if you are fairly sure your refrigerant charge is sufficient. Otherwise, see attached for the normal AC diagnostic steps. Good luck!

 

Also try resetting the system again. Pull the negative on the battery for 10 seconds and reconnect. Are you able to hear and or see the compressor engaging? RPM's increasing when turning AC on?

 

First - I forgot to mention that the rear seat A/C is working the same...no cold air.

Lavrishevo - I have had the negative battery cable disconnected several times as I was looking for a possible 'parasitic drain' which might have killed my previous battery (none detected - only 35 MAmps drain). Also, as I say in my original post, "The engine RPM clearly increases and decreases as the A/C is turned on and off".

StanVanDam - The self-diagnostic test also runs the system through 9 different modes of operation. I could hear the doors and motors working as the air flow was rerouted and fan speed changed. Your suggestion to cycle from full hot to cold really had my hopes up. However, I just ran it thru the full temp range twice.....no change. I'll now give your attachment a thorough read...I've been searching for that all day.

Thanks to both of you gentlemen...much appreciate your input. I'll let you know the results - Bill

 

There is only one compressor so I would start with that. It may be odd timing but the most common failure point is the compressor itself. Need to have the high and low side tested. I would consult an AC expert or have a Toyota / Lexus dealer diagnose the problem.

 

Did you check if compressor clutch works after switch AC on?

 

I had the same issue on my '01 last summer (coincidentally after tracking down an electrical gremlin requiring disconnect of battery). It was the A/C pressure switch located in front of the radiator right side low. https://www.clublexus.com/forums/ls4...n-and-out.html

 

First I have to say how impressed and thankful I am for all the knowledgeable advice.

I'll run the test procedure in the service manual (thanks StanVanDam). Then have my pressures tested (thanks Lavrishevo). If those tests are in normal range, I'll focus on the high pressure switch (Thanks Tom57).

Owczar - I have tried to hear the compressor clutch engage in the past (before my problem started) and, unlike my Nissan Maxima, I can't hear a similar sound.... just the engine RPM increasing and decreasing as the A/C is switched on and off (a very quiet clutch??). Is there another way to tell if the clutch is engaging? Will keep you posted - Thanks Again - Bill

 

You should take off inlet above radiator. You will see AC compressor and compressor pulley. When engine idling observe compressor pulley. After AC switch ON central part of pulley should start rotate.

 

I did as you suggested. The disk/hub attached to the front of the pulley turns with the pulley whether the A/C is on or off. That hub appears to be one piece with no separate center piece. Thanks Bill

 

The A/C compressor does not have a clutch. It is actuated by a solenoid.

 

I ran the Refrigerant Volume test in the service manual. At 1500 RPM, front & rear A/Cs on MAX, I'm now seeing lots of bubbles in the sight glass and feeling no temperature difference between the compressor inlet and outlet pipes.......indications of low refrigerant level and probable leak. Will have it leak tested today.

 

You`re right. My mistake. Clutch has LS430 between 2000-2003.

 

You owe me a cookie

 

At the earliest opportunity

You shoul check rear AC for refrigerant leak.
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