Question about 2003 Chevrolet TrailBlazer

1 Answer

Loud thumping noise in rear air

My 03 Trailblazer EXT is making a loud thumping noise in the rear air compartment, but when I remove the fuse for heat/air B it stops. What is making this noise and will it be expensive to reapair?

Posted by on

  • 1 more comment 
  • kirker09 Dec 08, 2008

    I have a thumping noise that sounds like an air actuated or electrical valve coming from teh right rear passenger side interior panel where the rear air handling stuff is located. It starts after teh engine is on and continues for a couple of minutesd then stops. It does this every time I stop and restart the engine. SOunds like a controller issue or a damper valve hanging up. Definitely sounds like an air pump-like thumping.

  • Marvin
    Marvin May 11, 2010

    Have a GM tech listen to the noise, this is a new one on me.

  • Robert Wright Oct 14, 2012

    I have a loud thumping noise sound when I turn on the heat which is coming from fron



1 Answer

  • Level 2:

    An expert who has achieved level 2 by getting 100 points


    An expert that gotĀ 5 achievements.


    An expert that hasĀ over 500 points.


    An expert who has answered 200 questions.

  • Expert
  • 255 Answers

Hi, you should check if the blower plastic fan is rubbing against the fan housing ,they get lose with time and make those noises.good luck C1...

Posted on Nov 29, 2008


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

Hi there,
Save hours of searching online or wasting money on unnecessary repairs by talking to a 6YA Expert who can help you resolve this 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.

Here's a link to this great service

Good luck!

Posted on Jan 02, 2017


Add Your Answer

Uploading: 0%


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



Related Questions:

1 Answer

Have a clicking noise in the right rear panel of my 2006 Envoy xl. Have had a new battery installed and a new alternator. The noise stays on all the time when the key is turned on . HELP!

That is a electrically controlled actuator for the rear HVAC - heating ventillation an air conditioning system . Mode door or temp. door actuator . They are plastic an the gears wear an strip .
Loud clicking sound from rear of 2003 Trailblazer EXT
2004 Chevy Suburban Rear Air Temperature Actuator Blend Door HVAC You would have to do the same thing to replace yours .

Jun 06, 2017 | Cars & Trucks

1 Answer

03 trail blazer ext. when going down the road from out of no where comes a loud grinding clicking metal on metal noise

If the noise you are referring to is coming from the front, it may be the guy assembly. Easy way to check, lift the front of the car and rotate each wheel by had, if you hear the grinding, your huh assembly needs replacing. Local automotive parts store usually have them in stock for around $104 but if you have a few days to wait, Rock can get them to you in a few days for 1/2 the price.

Apr 30, 2017 | 2003 Chevrolet TrailBlazer

1 Answer

2005 Ford Expedition: Constant thumping sound from dash when air/heat is on or off

Usually this is caused by a binding blend or mode door. The actuator keeps trying to move it and can't. Locate the exact source of the noise. Then disconnect the actuator and try opening and closing the door by hand.

Feb 28, 2018 | 2005 Ford Expedition

1 Answer

Rear HVAC unit in 2002 trailblazer making loud poping noise and then quits after a couple of minutes

The only thing i can think this would be is a blower motor noise, have shop take a listen is my best advice.

Oct 25, 2012 | 2002 Chevrolet TrailBlazer

1 Answer

Loud clicking noise from rear

If you have the EXT model Trailblazer, the clicking you hear is from the rear HVAC system and likely is one of the mode actuators trying to move a control door. The rear system is located behind a plastic panel in the rightside cargo area.

Oct 08, 2012 | 2002 Chevrolet TrailBlazer

1 Answer

03 monte carlo AC loud noise

If it is coming from the engine compartment it may be the clutch on the compressor.

Sep 05, 2012 | Cars & Trucks

1 Answer

Loud humming noise

The power steering pump humms when it has gone bad.

You need to replace or service it incase there is a blockage due to dirt in the transmission oil compartment.

Costs not so much.

Rate this please.

May 23, 2009 | 2003 Chevrolet Trailblazer Ext

1 Answer

04 Trailblazer ext Loud sound

CV-joint (axle) but most likely the wheel bearing like mentioned. When you turn right the weight shifts to the left taking the load off the right passenger side bearing.

May 14, 2009 | 2004 Chevrolet TrailBlazer

1 Answer

2005 expedition rear a/c makes thumping noise when transferring

Sounds like the roof/floor actuator internal gear is stripped. The only way to fix it is to replace it. Remove the cup holder in the right rear trim panel. remove the 8mm bolts holding actuator and replace.

Feb 01, 2009 | 2005 Ford Expedition

Not finding what you are looking for?
2003 Chevrolet TrailBlazer Logo

505 people viewed this question

Ask a Question

Usually answered in minutes!

Top Chevrolet Experts


Level 3 Expert

81424 Answers

Colin Stickland
Colin Stickland

Level 3 Expert

22359 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