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Discussion in 'Chevy Trailblazer Forum (GMC Envoy)' started by corvetteman, Jan 13, 2014.

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  1. corvetteman

    corvetteman Member

    Just started today there is a very loud noise coming from the center of the dashboard. It sounds like a big clock TICK TOCK, TICK TOCK. Any idea what is causing this.
  2. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    It could be one of the heating/cooling system actuators. There would be one to change the temp for the passenger, one to change the temp for the driver and one to change the direction of the air flow (floor/dash/vent). If they get stuck, they make a clicking sound trying to reset.

    Try a battery disconnect for 30 seconds to see if it resets. If it won't, you probably need a new one.

    Second possibility, is the radio unit; do you have the nav radio by any chance?
  3. corvetteman

    corvetteman Member

    Have the Bose radio and it's not a ticking sound its a loud banging noise like something is hitting on something. Would an actuator do this? How do you remove the dash pad to get inside to see what's going on? Thanks
  4. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    I'd get under the dash and try to find the source of the noise. I use my hand and when you get close, you can usually feel the noise in your finger tips.

    After I posted the first response, I remembered that there was a change from vacuum to electric actuators somewhere around 2000. I don't remember which kind you have.

    An additional thought, do you get this noise only when the blower motor is running?
    Could it be something related to this motor?
  5. corvetteman

    corvetteman Member

    Just went out and confirmed it has to do with the HAVC system. It makes the noise when the defroster and defroster/heat modes are selected I put it on heat/vent and the noise went away. Put it back on heat/defrost and it started up again.
  6. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    Ok, that is the mode actuator. Again, I don't remember if you have the electric ones, or the vacuum motor. From the description, I suspect the electric ones.

    Try the battery disconnect/reconnect and see if that will reset the actuator.
  7. corvetteman

    corvetteman Member

    Haven't had a chance to disconnect the battery yet but if that doesn't work how do you get at the defrost actuator? It seems to be the culprit.
  8. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    I can't help you with that truck, but you might find a "how-to" on Youtube.
  9. corvetteman

    corvetteman Member

    Thanks! You pointed me in the right direction.

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