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2004 chevy trailblazer_ls_ext
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Discussion Starter #1
2004 4.2L Trailblazer EXT - Blower motor not working on Fan position 5, works on all others 1,2,3,4. No voltage at blower motor resistor from 40A fused circuit and fuse 35 is good under hood. Voltage is at fuse but not at connector on blower motor. i get voltage on relay when on fan position 5. a break somewhere in wiring? cant trace back! how do i check or rewire with another 12v source? HELP!
 

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2004 chevy trailblazer_ls_ext
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6 Posts
Discussion Starter #3
Maybe bad or dirty connections .
nothing on wire going into connector. and cant trace back. Having a real difficult time findind after going into bundle under dash. have most of dash panels off now. There is no panels on drvers side at all now! I have schematics but don't know how to determine connectors inline if any are actually there. :undecided
 

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2008 chevy trailblazer_lt
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300 Posts
I think you just have to monitor the voltage coming out of the blower motor speed control switch. IF there voltage coming out for all but the 5 speed, then it is likely that the switch / control is bad. Otherwise, you can continue your trace of the wires from the switch to the resistor pack.

NOTE: there are separate wires running between the blower control and the resistor pack and that the highest speed does not pass thru any resistors. Further that the fan relay needs to operate for the highest speed. It is NOT energized for the other speeds. I am not sure that I understand your initial "test observations" about the relay and about voltage from the 40 amp fuse.... that voltage goes to the fan relay (switched contact) and not to the resistors. In high speed settings, the relay should see TWO 12v conditions at the relay, one for the coil and one for the feed to the motor.... unplug the relay and measure for these at the holder.... plus you should hear / feel that the relay is operating... PLUS of course, you need to have the ground condition also on the coil.
 

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2004 chevy trailblazer_ls_ext
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Discussion Starter #5
The voltage through the switch is fine.. I get voltage out on all 5 positions. The 5th position sends 12 volts to the resistor pack to energize the relay to allow the 12v 40 Amp feed to fire the motor. I have no 12volts on pin G on resister pack connector. This voltage (from what I can tell on schematic) comes directly from fuse 35 under the hood.. the connector at resistor pack looks like it was already replaced.. SO, I checked for the voltage before the splice of the new connector and it is NOT there either.
 

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2008 chevy trailblazer_lt
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300 Posts
OK... good work.... have you checked for voltage on both sides of the 40amp fuse.... probably but lots of people just assume that a good fuse means good voltage. Further, with the fuse removed, measure resistance from the fuse "far side" towards the fan relay. It should have some form of resistance, not open or short.... from there start wiggling wires to see if that changes. Of course, finding the wire output from the bottom / connector on the fuse box is tough but that is probably your next stop.
 

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2002 chevy trailblazer_ls
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Same thing for me some years ago. I change dash panel and it's perfect now.

on ebay is less expensive sometime.
 

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2004 chevy trailblazer_ls_ext
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Discussion Starter #8 (Edited)
Went to junk yard (Crazy Ray's) and finally found a cadaver TB.. I practiced taking the under hood fuse box off (lifted up , not really off) and found the connector for fuse #35.. I bought the connector and a few extra fuses too.. I MAY just pull the fuse panel up and install another feed wire through and give up trying to find the short in the old one.. All the while, PRAYING, that I don't screw anything else up!! I HATE electrical problems.. Kind of afraid to pull the battery cable off again.. Lost a Mode Door Actuator the first time I removed the battery.. what a PAIN!!!!
 

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2004 chevy trailblazer_ls_ext
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Discussion Starter #9
Got IT!

Flaky connection under the fuse box in engine compartment.. I took the part that I had gotten from junk yard and plugged it into bottom of fuse box..turned key on and had voltage there.. put other connector back on and now have voltage AND high at blower.. FAN Position # 5 working again! Now to fix the Mode Door Actuator that failed when I removed the battery terminal to test! :(:thumbsup:
 

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2008 chevy trailblazer_lt
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300 Posts
great / good.... clean the connection as best you can, then add some dielectric grease to keep it good and hopefully you will have solve your problem for good. Possibly check the pin "mechanicals" to make sure things are ok.
 
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