Heater - A/C Fan Control Switch - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum



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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > OEM Issues

OEM Issues Original Equipment Repairs and/or Problems

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  #1  
Old 12-13-2004, 10:24 AM
Twins03 Twins03 is offline
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Heater - A/C Fan Control Switch

All of a sudden, my 1-3 speeds stopped working on my blower. 4 and 5 still work just fine. When I turn the swith to 1-3, the lights turn on as if it works, but nothing blows. Any ideas? Any suggestions? Vehicle is out of warranty and the dealer is awful.

Thanks
Scott
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  #2  
Old 02-16-2005, 09:39 PM
adamjeeps adamjeeps is offline
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Blower Motor resistor

I believe this is your problem. Should be a cheap part but might be a pain to replace yourself. Not sure where it is on the TB.
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  #3  
Old 02-17-2005, 09:47 AM
04TBEXT 04TBEXT is offline
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2004 Chevy TrailBlazer LS EXT
Dark Green Metallic 4.2L I6 4X4
Join Date: Feb 2005
Location: NORTHERN ILLINOIS AREA
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BLOWER MOTOR RESISTOR R&R

THE BLOWER MOTOR RESISTOR CAN BE SERVICED SEPARATELY. THIS RESISTOR IS LOCATED IN THE RIGHT SIDE OF THE HEATER CASE FROM INSIDE THE OF THE PASSENGER COMPARTMENT. THIS IS FOR A STANDARD (NON-AUTO) HVAC SYSTEM. TO R&R THE RESISTOR:
REMOVE THE RIGHT SIDE BLACK PLASTIC CLOSE-OUT PANEL UNDERNEATH THE I/P @ THE GLOVE BOX. IT IS HELD IN BY TWO SCREWS @ THE LOWER EDGE OF THE I/P AND HAS A FLAT TAB WHICH FITS INTO A SLOT IN THE FIREWALL. ONCE REMOVED, LOOK ON THE HEATER CASE FOR A RECTANGULAR BLACK PLASTIC PIECE (APPROX. 2" X 5") WHICH IS HELD IN BY TWO SCREWS; (1) EACH OF THE LONG SIDE OF THE RECTANGLE. YOU WILL FIND A FLAT SEVEN PIN CONNECTOR PLUGGED INTO THE RESISTOR. THE RESISTOR ALSO HAS A TWO-WIRE PIGTAIL (WIRES SHOULD BE PURPLE & BLACK) EXITING THE SIDE OF THE RESISTOR OF APPROX. 6". IGNITION MUST BE OFF (I RECOMMEND DISCONNECTING THE BATTERY AS SOME VEHICLE MODULES STAY POWERED UP TO 4-5 HOURS AFTER THE LAST IGNITION SHUT DOWN). THIS IS SPECIFIC OF T/B WITH AUTOMATIC DUAL ZONE CLIMATE CONTROL STYLE HVAC SYSTEMS. DISCONNECT BOTH WIRING PLUGS, R&R THE (2) SCREWS HOLDING THE BLOWER RESISTOR IN AND THEN REVERSE THE PROCEDURE. IF YOU POST THE LAST 8 CHARACTERS OF YOUR VIN, I'LL GIVE YOU THE PART NUMBER.
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Old 06-14-2005, 07:44 PM
mvftw mvftw is offline
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04TBEXT, I have Dual Zone, Auto Climate in a '03 LTZ. All the fan speeds don't work. I believe it's the resistor module (I checked the blower fuse). Is it part # 52495874? Also are you saying that I have to disconnect the 2 wires, then unscrew it?
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Old 06-14-2005, 08:02 PM
coastie22 coastie22 is offline
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Join Date: May 2005
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speed 5 is busted on mine.all other are fine.
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  #6  
Old 01-14-2007, 12:29 PM
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TA Dave TA Dave is offline
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2002 Chevy TrailBlazer LS
Victory Red 4.2L I6 4X4
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Location: Rochester, MI
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Resistor replacement notes - update.

Thanks to 04TBEXT - I followed your instructions and now my heater fan works great! That's especially important here in Michigan at this time of year.

One noteworthy item - the new resistor had a plastic rectangle on one side that made it impossible to install in original orientation (we call this mistake-proofing in the industry). When I installed it backwards, the blower motor power wire wouldn't reach the motor. Also, the 7-pin connector would be practically impossible to remove if I ever did this again because the positive lock clip would be facing the firewall, not the interior.

I ended up cutting off this rectangle with a Dremel tool and installed it in the right orientation, and all worked perfectly.

Last note - you need a 7mm (I didn't check for a US equivalent) socket to remove the close-out panel and a 7/32" socket to remove the resistor itself. They are screws, but hex-headed, not phillips.

TA Dave
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  #7  
Old 11-19-2010, 04:16 PM
Tymatooltime Tymatooltime is offline
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2004 Chevy TrailBlazer LS
Summit White 6.0L LS2 V8 4X4
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AC/Heater Control switch

I lost fan speed #5 in the Trailblazer I had 1 thru 4. I read the comments in the forum. It seemed unlikely but I thought I would start with the blower motor resistor. It is easy to get to and costs under $30 dollars at Checker, Autozone etc... However, when I have encountered problems with a BM resistor in the past it usually takes out the lower speeds and all you get is high. I still felt it was worth the gamble. Picked one up for $27 at Checker auto. Followed the instructions posted earler. I have all 5 speeds again.

If you try this and it doesn't work:
You should also check fuse # 35 under the hood. It controls the high speed on the blower.

If it is not the fuse and not the resistor it will most likely be the fan switch. You cannot get a switch you need the whole module. Try ebay or a bone yard. Manual controls run approx $50 to $70. Digital runs more. This is a great deal....they are over $200 new.

Hope this helps others.
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