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2005 chevy trailblazer_lt
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Discussion Starter · #1 ·
anybody have a clue on why the auto control fans for the front and rear either stop, slow down when fan increased, pulse on and off higher lower speeds. the fan would be set on high but no blow then it works slowly and then all of the sudden works fine. resistor packs? fan switch(although the rear worked when front didnt and vice versa. Thanx for the help
 

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2004 gmc
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26,181 Posts
Resistor pack or the connector harness it gets wired to. They overheat and die. Relatively cheap and easy to locate at the local parts stores.
 

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2005 chevy trailblazer_lt
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Discussion Starter · #3 ·
ok ill check the harness or packs out. also noticed when TB started and the fan isnt working i shut off the C.C. system and then turn on and it works. the rear seat fan still works.... is it the harness or the pack that gets bad and if so is harness dealer item and resistors can be bought at part stores?
 

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2004 gmc
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Harness is available at parts stores as well.

Since the harness plugs into the resistor pack, you cannot tell WHICH is bad unless you have a meter or look very closely. They go bad together. There's a thread you should locate and read with "resistor pack .... pics" in the title.(advanced search lets you restrict search to the titles or the body)
 

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2004 gmc envoy_slt_xuv
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anybody have a clue on why the auto control fans for the front and rear either stop, slow down when fan increased, pulse on and off higher lower speeds. the fan would be set on high but no blow then it works slowly and then all of the sudden works fine. resistor packs? fan switch(although the rear worked when front didnt and vice versa. Thanx for the help
Remember, if you have the Auto Controls, the part is called a Fan Control Module, and the wire harness is different. There is also a newer design part that replaces the module on many vehicle models and requires some slight changes in the wiring. Full instructions will be included if you get the Universal Module.
 

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2005 chevy trailblazer_lt
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46 Posts
Discussion Starter · #6 ·
replaced trhe module with a new updated module and wiring harness/plugs....12volts to the blower and it spins...the module either defective or something else wrong....put in old module and no nothing works....wondering if auto control panel? fan works when 12v put to it...new module is a Standard brand so good electronics and newer style pigtails....baffled..any suugestions?
 
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