A/C will not turn off 😑 - ClubLexus - Lexus Forum Discussion


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A/C will not turn off 😑

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Old 09-21-16, 03:23 PM   #1
Kdfwagen
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Default A/C will not turn off 😑

I just purchased a 1996 LS400 with 180k. Everything works on the car. However the air conditioning will not turn off... Lol. I first noticed this problem when I was commuting and I had the AC button off. When I got out of the car there was a ton of water dripping from the two AC condensation drain hoses under the car. Also when I opened the engine bay I could see the AC lines had condensation all over them.

I tried turning off the AUTO mode... Turning the AC switch off... Turning the temp up to 77 degrees...but the AC still runs and condensation builds up.

I visually checked the compressor and it is running. I can see the ?clutch? On the outside spinning. However if I disconnect the relay for the AC clutch it stops spinning and the AC turns off.. I also tried switching the relay with another but the AC still runs when turned off and I can visually see the clutch is engaged/spinning. What should I check next? It would be nice to turn off the AC to save some mpg on my commute..

Thank you for reading.
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Old 09-21-16, 04:48 PM   #2
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You need the procedure to run the diagnostics on the control, I don't know if is different from the Gen 1's. The control is suspect.
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Old 09-21-16, 06:48 PM   #3
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It doesn't seem like a common problem. I can't find anything on the internet about the AC constantly running in a car or not being able to turn it off. I really don't want to take it to the dealer. My carista app shows 0 fault codes.
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Old 09-21-16, 08:06 PM   #4
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I hate to break it to you, but the internet does not have all the answers to everyones problem!

As dicer said, run a DTC check on your AC control unit. With the ignition off, simultaneously hold the AUTO and recirculation buttons together, and turn the ignition to ON. It will first test the indicators, then go into a diagnostic trouble code test. Codes will be shown on the right side of the display, i think from like 11-42.

Do this and report back if you received any DTC's. It will beep during the DTC display if the trouble is currently present, and not beep if the trouble code is a history code that isn't currently faulting.
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Old 09-21-16, 08:18 PM   #5
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Quote:
Originally Posted by Banshee365 View Post
I hate to break it to you, but the internet does not have all the answers to everyones problem!

As dicer said, run a DTC check on your AC control unit. With the ignition off, simultaneously hold the AUTO and recirculation buttons together, and turn the ignition to ON. It will first test the indicators, then go into a diagnostic trouble code test. Codes will be shown on the right side of the display, i think from like 11-42.

Do this and report back if you received any DTC's. It will beep during the DTC display if the trouble is currently present, and not beep if the trouble code is a history code that isn't currently faulting.
I was told the 95+ ls400 don't have this DTC check. I tried it earlier today just for the hell of it and nothing showed up, blinked, beeped, or codes on the display.
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Old 09-21-16, 09:30 PM   #6
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I was told the 95+ ls400 don't have this DTC check. I tried it earlier today just for the hell of it and nothing showed up, blinked, beeped, or codes on the display.
What you were told is incorrect. Hold the AUTO and the button with the icon of the car with the 180 degree U-shaped arrow inside the car then turn on the ignition.
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Old 09-21-16, 09:41 PM   #7
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Things are not very simple. You need to know that the magnet clutch of the A/C compressor is controlled by the main ECU. Pin #13 of the main ECU connector E is the drive line of it. The main ECU receive the signals from the HVAC/Navi unit at the pin #20 of the connector E and the pin #10 of the connector F. In order to distinguish the problem, you need to observe these if there's no code.
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Old 09-21-16, 10:40 PM   #8
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Quote:
Originally Posted by Banshee365 View Post
What you were told is incorrect. Hold the AUTO and the button with the icon of the car with the 180 degree U-shaped arrow inside the car then turn on the ignition.
Ok you are right I got it to work just now. I get the code: 21 & 24. there is a single beep when each number flashes. I found code 21 which is for a solar sensor (it's dark out right now) but I have no idea what code 24 is. Anybody know?
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Old 09-21-16, 10:41 PM   #9
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Code 24 is drivers solar sensor. Both codes are normal when DTC check is ran without sunlight on the sensor. You essentially have no codes. You quite possibly have a bad ac control unit.
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Old 09-21-16, 10:50 PM   #10
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Code 24 is drivers solar sensor. Both codes are normal when DTC check is ran without sunlight on the sensor. You essentially have no codes. You quite possibly have a bad ac control unit.
Funny how everything works on the unit.. besides maybe the AC on/off. The recirc, fan speed, heat, and air flow direction all work.. maybe a faulty solder? Cracked..?
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Old 09-21-16, 11:05 PM   #11
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How comfortable are you in removing the unit from the dash to access the connectors for back-probing? You'll need to trace the circuit to see where the fault it. It could be wiring, the AC control unit, or main engine computer.
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Old 09-22-16, 12:08 AM   #12
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I just need a DIY for the removal.. I always break interior pieces when I try to figure it out on my own
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Old 09-22-16, 01:06 AM   #13
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How to Lexus LS400 car radio Stereo Removal 1995 - 2000 replace repair display - YouTube

I don't know but there maybe capacitors in there that can go bad. Maybe Yamae knows, and you need to do what he says. He is very good at the electronics on these cars. Oh and don't do what he does and leave the key on and the battery connected.
If there is no release button for shifter, first disconnect the battery then do the key and put it in the position to remove stuff. Just remember to remove the key before reconnecting the battery. Super NO NO leaving the power on to it while unplugging stuff. Don't do that, and maybe why its not working, someone could have done that. DISCONNECT THE BATTERY FIRST !!!!!

Last edited by dicer; 09-22-16 at 01:14 AM.
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Old 09-22-16, 12:44 PM   #14
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before you go to all that trouble, make sure your defrost button is not faulty and staying on... it would run the AC also.
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Old 09-22-16, 03:06 PM   #15
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So somehow someone messed the link up to the youtube deal it won't work now.
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