Question about Chevrolet TrailBlazer

1 Answer

How to reset the HVAC mode actuator,becaoused my dash vents seem no airflow coming out.

Posted by on

  • Paul Marshall
    Paul Marshall Apr 06, 2009

    No air coming out of the dash vents, only the defrost and floor. There was a clicking noise before it quit all together. Could it be the HVAC mode actuator?



1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points

    Top Expert:

    An expert who has finished #1 on the weekly Top 10 Fixya Experts Leaderboard.


    An expert that got 20 achievements.


    An expert that got 10 achievements.

  • Chevrolet Master
  • 77,169 Answers

You have a problem with mode mode control switch, it is either leaking vacuum or has no vacuum to it, all of the different modes are switched using vacuum operated air door motors to send air to the selected outlet, i.e. floor, dash. defrost or a mix.

Posted on Oct 17, 2008

  • yadayada
    yadayada Oct 20, 2008

    This rating is unjust based on your question and my 30 years of automotive experience the answer is correct. What answer did you want, there is flat no such thing as a HVAC reset, please change the rating to a more appropriate Helpful.



1 Suggested Answer

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

a 6ya expert can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of.(from cars to computers, handyman, and even drones)
click here to download the app (for users in the US for now) and get all the help you need.

Posted on Jan 02, 2017


Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

1 Answer

What makes a Clicking noise coming from dash board on the passenger side?

Possibly an actuator in your HVAC system. There are actuators to move the blend door, mode door, recirc door, and possibly others depending on your HVAC options (climate control, dual control, etc). With your car running, can you change the temperature from cold to hot and back, and can you direct airflow to floor, defrost, and dash vents? When you select recirculate (max a/c), can you hear the change? If you have problems with any of these, you may need to replace an actuator or one of the doors may be jammed.

Jul 25, 2017 | Chrysler Cars & Trucks

1 Answer

My 2002 Cadillac Deville won't blow air directly to my face out of the vents, please help.

Center vents not working , is this what your saying ? Air comes out of the defroster vent or floor vent only ? Mode door stuck or mode door actuator bad !
Mode and Recirculation Actuators The mode and recirculation actuators are 2-wire bi-directional electric motors. Two control circuits enable the actuators to operate. The control circuits use either a 0 or 12 volt value to co-ordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 12 volts. In order to move the actuator, the HVAC control module grounds the appropriate control circuit for the commanded direction. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction.
The HVAC control module(IPM) determines the door position by counting motor pulses on one of the control circuits. These pulses are small voltage fluctuations that occur when the brush is shorted across two commutator contacts as the motor rotates. As the actuator shaft rotates, the HVAC control module(IPM) monitors the voltage drop across an internal resistance to detect the pulses. The HVAC control module(IPM) converts the pulses to counts with a range of 0-255 counts. The HVAC control module(IPM) uses a range of 0-255 counts to index the actuator position.
If the problem is the actuator the instrument panel has to be removed to replace it . Your best bet is to take your vehicle to a qualified repair shop .

Jun 28, 2016 | Cadillac Cars & Trucks

1 Answer

The air only comes out of the circle vents on dash, not the defroster vents or floor vents. I have a 2005 Pontiac G6 base model and I am not sure how to fix this issue

In side you dash is a electronically controlled actuator call a mode actuator , it controls which vents the air comes out of ! They go bad, plastic gears in side of it wear out, a lot of times you'll hear a clicking sound in the dash. They are not to tough to fix ,you need to take Instrument Panel Insulator Panel off - Left Side under dash . Some times stuff drops down in an binds up the door inside .Have a little child , they like putting stuff in the vents ,pencil's an the like.
Mode Door Actuator Dorman 604 121 Controls Airflow Direction

Jan 10, 2015 | 2005 Pontiac G6

1 Answer


  • Do you hear any clicking noise form in the dash ? Sounds like the mode door actuator mite be bad or stuck or the HVAC control module isn't controlling it. The ford service repair information manual has a long drawn out test procedure PINPOINT TEST B: INCORRECT/ERRATIC DIRECTION OF AIRFLOW FROM OUTLET(S) You would have to take some of your dash apart to get at the wiring connectors on the back of the HVAC control module . You need a volt- ohm -meter to do some testing : first thing is to
  • Dec 20, 2014 | 2005 Ford Mustang V6

    1 Answer

    No air coming out the dash vents. Air does come out the floor vents and defroster vents

    {: ) You didn't mention which vehicle model you have, but anyway, check and make sure your control setting is not on defog or defrost. When the HVAC system detects a fault or inconsistencies in the actuator feedback circuits, the HVAC module will default the position of the mode actuator to the floor vents. Usually the fault is caused by the mode actuator itself, or it could be that the actuator doors are blocked or binding, and wiring or terminal connections come next on the list.
    If it is an actuator door issue, the HVAC Blower Module should be removed and disassembled. And this also means removing the whole instrument panel which is a big job. I just hope your case doesn't go this far.
    For the meantime, what you can try is to recalibrate the actuators. Turn a/c and ignition off. Turn ignition on and wait forty seconds ( don't move any HVAC controls during this period). Afterwards, you may start the engine and check operation. If not successful, a scan tool is the next option, to retrieve any codes set, and to perform actuator recalibration.

    Jul 15, 2011 | Chevrolet Silverado 1500 Cars & Trucks

    2 Answers

    I changed the battery on 2006 Trailblazer SS. Now I can only get AC from my windshield and floor vents. Nothing from the dash vents. Also the temp control only gives coldest temp. I have checked fuses...

    once you disconnect the battery your body control module loses power and memory you have to get some one with a scanner with reprogramming capabilities and have the computers reset ,dealer?

    Aug 05, 2010 | Chevrolet TrailBlazer Cars & Trucks

    1 Answer

    2006 slt gmc envoy ac problems vent controls anbd

    {: ) The popping sound you heard is caused by the sudden movement of an HVAC door, most probably coming from the recirculation door actuator (right dashboard area) or the mode actuator( mid dashboard area). The fan outputs could be normally working, but is being muffled by the incorrect positioning of the HVAC doors, giving an impression that there is fault in the blower controls. In other words, your vehicle is having an air distribution issue.
    If there's no conflict in your climate settings, then the trouble may be in the HVAC doors binding or broken, or the actuators faulty or sticking. In both cases, servicing may involve removal of the dashboard to access these HVAC components.

    Jul 20, 2010 | 2006 GMC Envoy

    1 Answer

    Location and removal of the air vent actuator. step by step on how to get to it and replace it. Air blows and I can control hot and cold but I cant change from floor to vent to dash. It just keeps blowing...

    Removal & Installation
    1. Remove the floor air outlet duct extension from the floor duct.
    2. Remove the center console, if equipped.
    3. Remove the screws from the center console duct, if equipped.
    4. Remove the center console duct, if equipped.
    5. Disconnect the electrical connection at the mode actuator.
    6. Remove the mode actuator mounting screws from the HVAC module.
    7. Remove the mode actuator as an assembly with the actuator cam.

    Mode actuator location

    To install:
    1. Install the mode actuator as an assembly with the actuator cam.
    2. Line up the heater/defroster valve lever with the mode actuator cam slot.
    3. Line up the A/C valve lever with the mode actuator cam.
    4. Install the mode actuator mounting screw to the HVAC module and tighten to 14 inch lbs. (1.6 Nm).
    5. Connect the electrical connection at the mode actuator.
    6. Install the center console duct, if equipped.
    7. Install the screws to the center console duct, if equipped, and tighten to 14 inch lbs. (1.6 Nm).
    8. Install the center console, if equipped.
    9. Install the floor air outlet duct extension to the floor air duct.
    10. Calibrate the HVAC module actuators.

    Apr 18, 2010 | 2004 Chevrolet Tahoe

    1 Answer


    Chevrolet 2003 TrailBlazer

    For a digital air flow system try resetting the HVAC unit. Either take out the fuse for the HVAC module or disconnect the battery for 5 or 10 minutes. Reconnect battery or replace fuse. Turn the ignition to ON and DO NOT STARTor ATTEMPT to START ENGINE !!. You should hear the actuators, motors etc resetting. This should take about 2 minutes . Then you can start engine. If this does not work, you may have a bad actuator under the dash.

    Jun 07, 2009 | 2003 Chevrolet TrailBlazer

    2 Answers

    Dash vents will not blow air

    It may be the mode actuator. Have you heard any clicking or other strange noise ? Under the drivers rear seat, in a plastic box is a fuse panel. Remove the two retainers, and the cover. Remove the HVAC or A/C fuse for a minute or two. Reinstall the fuse and this will make the A/C system relearn. Whwn you put the fuses back do not touch the A/C controls. Start the truck and leave it run for two or three minutes. Then try to change the vent from floor to vent and defrost. If this does not work you will need a mode motor. Good Luck

    May 22, 2009 | 2006 GMC Envoy

    Not finding what you are looking for?
    Cars & Trucks Logo

    Related Topics:

    2,174 people viewed this question

    Ask a Question

    Usually answered in minutes!

    Top Chevrolet Experts


    Level 3 Expert

    77169 Answers

    Colin Stickland
    Colin Stickland

    Level 3 Expert

    22258 Answers

    Ronny Bennett Sr.
    Ronny Bennett Sr.

    Level 3 Expert

    6927 Answers

    Are you a Chevrolet Expert? Answer questions, earn points and help others

    Answer questions

    Manuals & User Guides