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2002 gmc envoy_sle_xl
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Discussion Starter #1
Two weeks ago, I had the blower resistor changed because fan speeds 1 and 2 had quit working. That fixed that problem.

Now, when I turn the knob to adjust the air flow through the vents, nothing happens. It seems to be stuck on the last position I had it on (top and bottom). Although the fan is working, hardly any air comes out of the vents.

Also, when I turn on the engine for the first time, a rat-a-tat clicking noise can be heard from the middle of the dash. This goes on for a few seconds, stops, then starts again, then stops, then starts again. Finally, it stops.

So . . . anyone have a diagnosis? Could it be the actuator? Fan speed module?
Thanks for your help. (BTW, I have approx. 76,000 miles on my 2002 Envoy.)
 

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2002 gmc envoy_slt
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Sounds like a bad mode actuator. Check out the thread in the stickies called "HVAC Mode Actuator Door Replacement". If you unhooked the battery while doing the resistor pack repair it most likely caused this to fail. There is a reset method to try first, but I don't remember the sequence. It is in the thread mentioned above.

I just replaced my driver's side temp actuator. Lukily it is the easiest to get to. In my reading I thought I had to pull my center console so it added a little time that wasn't really necessary. (But I did get to clean under the center console). Just pull the front and underdash panels, don't waste your time on the center console. HTH c good
 

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2002 gmc envoy_sle_xl
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Discussion Starter #3
Thanks

Thanks. Don't know if the guy disconnected the battery when he installed the blower resistor. Either way, I have the problem. Now to get it fixed. Wish I could do this myself but lack the tools and the knowledge. From reading the other posts, others have had similar experiences.

Just curious, do you know if that rat-a-tat sound I hear is indicative of a failing mode actuator? Thanks, again.
 

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2002 gmc envoy_slt
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Dealer or other shops may want big bucks ($800-$1000) and insist they have to disassemble the dash to replace the mode actuator. This is no longer the case given a special tool that allows the tech to remove actuator from below with a "puller/press". Special Tool #GE-47676. There is a GM TSB but don't know that # offhand. It's in the 40 pages in the sticky somewhere. I know I saw it, I read all 40 pages from top to bottom. (I have no life!):D:D c good
 

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I HAD THE SAME RAT-A-TAT CLICKING NOISE AND THE AIR WOULD ONLY COME OUT OF THE FLOOR VENTS AND NOT THE DASH VENTS. THE CLICKING NOISE IS FROM THE TEETH MISSING ON ONE OF THE PLASTIC GEARS INSIDE ONE OF THE THREE ACTUATORS UNDER THE DRIVERS SIDE DASH NEXT TO THE CENTER CONSOLE. REMOVE THE COVER OF THE ACTUATOR TO SEE THE PLASTIC GEARS. ONCE YOU FIND OUT WHICH ACTUATOR GEAR IS BAD, ORDER THAT WHOLE ACTUATOR ASSEMBLEY ( $79 FROM GM) AND JUST SWAP THE NEW GEAR OUT FOR THE GEAR WITH THE MISSING TEETH. ITS ALOT EASIER THEN REPLACING THE WHOLE ACTUATOR AND YOU HAVE SPARE GEARS FOR FUTURE USE.:thumbsup:
 
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