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car A/C varying air flow

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New User

Aug 9, 2017, 9:46 AM

Post #1 of 3 (299 views)
car A/C varying air flow Sign In

I have a Toyota Land Cruiser, Year 2000 model, with 170,000 km on ir. The air flow from its A/C goes up and down. When air flow falls, it is still cold, no problem there. But when air flow goes down, even the flow sound changes. Then when flow goes up, again the sound changes, as if a valve has opened or a seƱsor has opened a valve and increased flow. So, the a/c air flow kind of cycles. Could any one help as to what the problem might be? Is it some sensor malfunctioning or a faulty fan unit, etc?

Ultimate Carjunky / Moderator
Discretesignals profile image

Aug 9, 2017, 10:07 AM

Post #2 of 3 (297 views)
Re: car A/C varying air flow Sign In

If this has automatic temperature control, does this happen even in manual mode?

You may have to monitor blower speed signals and air door position sensors to get an idea if it is a door movement or blower speed changing. From there you would have to monitor HVAC data to see what sensors are reading and such.

Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Aug 9, 2017, 12:50 PM

Post #3 of 3 (276 views)
Re: car A/C varying air flow Sign In

You can pull AC codes manually on this unit if it has ATC.

Indicator Check

  1. Turn the ignition switch on while pressing the A/C switch and R/F SW simultaneously.

  1. Check that all the indicators light up and go off at 1 second intervals 4 times in succession.

  • After the indicator check is ended, the diagnostic sensor check begins automatically.
  • Press the OFF switch when cancelling the check mode.


  1. Perform an indicator check. After the indicator check is completed, the system enters the diagnostic sensor check mode automatically.
  2. Check the LED blinking on the panel. Refer to the list of codes when translating the trouble code from the LED blinking.
If the slower display is desired, press the A/C switch and change it to step operation. Each time the A/C switch is pressed, the blinking LED changes by 1 step.


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

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