Knocking Noise from the back passenge...

Knocking Noise from the back passenger inside panel

Posted in the GMC Envoy Forum

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Randy

Edmonton, Canada

#1 Nov 19, 2008
I have a knocking noise coming from the back area of my Envoy. I knocks for a while then goes away. I took it to my GM dealer & he had no idea so I thought I would ask around if any one else had this problem. It's not the speaker, rear window opener,we checked all the obvious things but the people at GM are confused as well.
Chirs

Tampa, FL

#2 Nov 25, 2008
I have a 2003 Isuzu Ascender (envoy) and mine is doing the same think. It only happens when I first turn on the ignition and lasts for about 30 - 60 seconds. Mine is coming from the Right Rear Panel in the cargo area. I would describe mine as a very loud "clicking" noise.

I wonder if the fuel pump is located there? My fuel gage also does not work when the outside temperature drops below 70 degrees or so. But, the low fuel warning light works?
Jim

Yorktown Heights, NY

#3 Nov 30, 2008
I have the same problem on my 04 Trailblazer that just started happening last week. My mechanic thinks that it's part of the rear ventilating system - there's some gear that's not meshing right - and grinding. The car doesnt have to be running - just the ignition on will do it. It stops after about 60-90 seconds. I was coming on here for some DIY help to fix it myself - it's finding it that takes some time.
Randy

Edmonton, Canada

#4 Jan 4, 2009
I took things apart & there is a solenoid that moves a damper. I wanted to replace it, went to a GM dealer to get a new one, a mechanic said it was the computor "HUNTING" to set the damper & needed to be re-calibrated. 4 hrs later they came to me & said it was the solenoid but they didnt have one, but they did have a bill for the labour to check the computor. I dont know why GM is in trouble when they can pull crap like that.
Alex

Napoli, Italy

#5 Apr 24, 2010
This noise comes from the rear air conditioner system. It's a small actuator that opens a damper or vent. Whe it goes bad it skips gear and that is were the knocking comes from. I replaced mine for about $40 and less than half hour of labor. The computer for the hvac is calibrated automatically when the ignition is turned on and left alone for a little over a minute. Aftr wards the system could be used normally and it should work if there is an issue with the settingns not corresponding to the settings in the control units. Disconnect the plugs from the rear of the control unit in the front and the one in the rear with the key out of the ignition. After plugging them back, start the car and let it run for a little over a minute. The system will calibrate itself and reprogram all controls. Hope this helps!!!
jason

Clarksville, TN

#6 Feb 19, 2011
Randy wrote:
I have a knocking noise coming from the back area of my Envoy. I knocks for a while then goes away. I took it to my GM dealer & he had no idea so I thought I would ask around if any one else had this problem. It's not the speaker, rear window opener,we checked all the obvious things but the people at GM are confused as well.


was u able to find out what the problem was , my wifes 05 envoy is now doin it
Jeff

Oxon Hill, MD

#7 Sep 30, 2012
Alex wrote:
This noise comes from the rear air conditioner system. It's a small actuator that opens a damper or vent. Whe it goes bad it skips gear and that is were the knocking comes from. I replaced mine for about $40 and less than half hour of labor. The computer for the hvac is calibrated automatically when the ignition is turned on and left alone for a little over a minute. Aftr wards the system could be used normally and it should work if there is an issue with the settingns not corresponding to the settings in the control units. Disconnect the plugs from the rear of the control unit in the front and the one in the rear with the key out of the ignition. After plugging them back, start the car and let it run for a little over a minute. The system will calibrate itself and reprogram all controls. Hope this helps!!!
Can this be fix without changing the actuator ?, thanks
Jeff

Oxon Hill, MD

#8 Sep 30, 2012
Can this be done with out changing yhe actuator ?, thanks.
jax

New York, NY

#9 Feb 2, 2013
wow just recently i have the same problem to no avail can anyone tell me whats wrong it knocks and then stop .........ive been researching some answers online some say it may be the alternator
Tyris

Shelbyville, TN

#10 Mar 21, 2013
Do you have a part # for the acruator? Email: tryrisgilmore@ gmail.com
Alex wrote:
This noise comes from the rear air conditioner system. It's a small actuator that opens a damper or vent. Whe it goes bad it skips gear and that is were the knocking comes from. I replaced mine for about $40 and less than half hour of labor. The computer for the hvac is calibrated automatically when the ignition is turned on and left alone for a little over a minute. Aftr wards the system could be used normally and it should work if there is an issue with the settingns not corresponding to the settings in the control units. Disconnect the plugs from the rear of the control unit in the front and the one in the rear with the key out of the ignition. After plugging them back, start the car and let it run for a little over a minute. The system will calibrate itself and reprogram all controls. Hope this helps!!!
Richard F

Birmingham, AL

#11 Apr 21, 2013
Tyris wrote:
Do you have a part # for the acruator? Email: tryrisgilmore@ gmail.com
<quoted text>
Did you ever get the part number for the actuator?
oldcargye

Kernersville, NC

#12 Apr 27, 2013
ac part#= 15-72811...GM part# = 88892975 = actuator both upper and side REAR vent ..04 envoy rearair..
bill

Allentown, PA

#13 May 8, 2013
Alex wrote:
This noise comes from the rear air conditioner system. It's a small actuator that opens a damper or vent. Whe it goes bad it skips gear and that is were the knocking comes from. I replaced mine for about $40 and less than half hour of labor. The computer for the hvac is calibrated automatically when the ignition is turned on and left alone for a little over a minute. Aftr wards the system could be used normally and it should work if there is an issue with the settingns not corresponding to the settings in the control units. Disconnect the plugs from the rear of the control unit in the front and the one in the rear with the key out of the ignition. After plugging them back, start the car and let it run for a little over a minute. The system will calibrate itself and reprogram all controls. Hope this helps!!!
hi, i have the same problem with the knocking noise i can see through the panel the actuator the problem is taking off the panel.did you have any trouble removing the panel? any information or help you can give me i would appreciate.
jackie

New York, NY

#14 Jun 20, 2013
trust me its the alternator guys
Bob H

Maywood, IL

#15 Jun 20, 2013
jackie wrote:
trust me its the alternator guys
Funny you say that, I just had the alternator replaced. Do you think the knocking was a precursor to the alternator going bad? I haven't had the knocking come back since the alternator was replaced, but it's only been 6 days. Thanks.
Debbie C

Andover, MN

#16 Aug 30, 2013
Along with the knocking for 30 sec when turning ignition on.....did any of you loose the air (hot or cold) coming out of the front vents?? It still comes out the side, feet, and front window vent but not the rest......
asd

Perryville, MO

#17 Sep 9, 2013
my 2005 envoy is knocking in the rear passenger side behind the panel. also my a/c went out in the front half of the envoy. is it the actuator?
Geneva

Monroe, MI

#18 Oct 3, 2013
I have an 2004 GMC ENVOY and I have knocking also to R rear panel area that began last week. Starts when I first turn it on--lasting 60 seconds or so..and its sooooo annoying!!! Is this something you can repair yourself if I purchased the part from above???--ie accuator
joe

Mercedes, TX

#19 Nov 13, 2013
2006gmc enoy make rattling sou between 45 50ph
aaron

Beloit, WI

#20 Nov 28, 2013
Mine did the same thing and I had dealship recalibrate the rear turning vane. Then My front when out approximately the same time. so I had to have the fixed too. it was the actuator in the front. Cheap part but a pain to get too. Also Recently I replaced my battery and now the rear vane need calibrated again. I am thinking it is bet to turn the air/vent system completely off before you unplug the battery..
Just my two cents.

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