Replacing Blower Motor Resistor

Discussion in 'Tech Info' started by nimrodcs, Apr 22, 2010.

  1. nimrodcs

    nimrodcs Full Access Member

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    I had to replace this the other day on my '97 Tahoe LT (4DR) and couldn't find a thread with pictures, so, here goes...

    Tools:

    • 7mm Wrench
    • 7mm Socket (1/4" Drive)
    • 1/4" Drive Ratchet (small as you can find)
    • New blower motor resistor ($17 at O'Reilly's)

    1. Gain access to the resistor by pushing in on the right side of the opened glove box. With a little effort, it should drop free. Lift it up off the hinges and set it out of the way.


    bmr1.JPG


    2. Looking through the glove box opening, you can see the HVAC box. Look on top of the HVAC box and a little to the left and you will see the blower motor resistor mounted snuggly.


    bmr2.jpg

    3. Unplug the electrical connector and begin removing the screws. I found it easier to start with the 7mm wrench to get it loose and then squeeze the ratchet in there to screw it out the rest of the way. There is a third screw on the front of the metal bracket to the left that will have come out as well.


    bmr3.JPG

    bmr4.JPG

    4. After removing the three screws and the metal bracket, pull the old resistor out, tilting it sideways and then sliding it toward you. You might bend the coils a little but this is ok.

    5. Your new resistor should come with a new gasket. Do not forget to put this on the new resistor. Tilt the new resistor sideways and slide it into position carefully (you might have to bend the coils gently again). Make sure it seats properly.

    6. Reinstall the two screws holding it in place (start with the wrench and tighten with the ratchet) and plug the electrical connector back in. If you want, you can reinstall the useless metal bracket. I left it out. I think it's suppose to hold a relay and the resistor in place, but I didn't see a need for it.

    7. Set your glove box back on the hinges and slam it closed. Your done.

    Now go have a beer.
     
  2. drowndindreams

    drowndindreams Full Access Member

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    did it come out dirty? only reason i ask is because it feels like my air doesn't blow as high as it used to.
     
  3. nimrodcs

    nimrodcs Full Access Member

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    It wasn't too bad. A little oxidation here and there.

    My blower motor is running constantly. It won't change speeds or turn off. I thought replacing this would fix my problem, but it didn't. Now I have to find time to pull the control unit out of the dash and look for corrosion or check the relays related to the blower.

    drowndindreams, yours could be the resistor or maybe your blower motor itself is going out.

    Here's the old resistor:

    bmrp2.JPG
    bmrp1.JPG
     
  4. fyremanpat

    fyremanpat Fyremanpat

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    was it running constantly before replacing the resistor? if not then you may have 2 of the coils touching on the resistor when you put it back in.
     
  5. nimrodcs

    nimrodcs Full Access Member

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    Yeah, I bought the 'Hoe back in 12/09 with the blower constantly running. Just got around to fixing it, hoping the resistor would solve it. I'm about 99% positive the coils aren't touching, though.
     
  6. nimrodcs

    nimrodcs Full Access Member

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    Well, I pulled the control unit out of the dash and found some pretty nasty stuff. There's a bunch of corrosion on the circuit board. The fan speed switch and the wire harness that plugs into it looks like they have gotten very hot at one point.

    hcu1.JPG

    fsc1.JPG

    fscs1.JPG

    I cleaned the circuit board the best I could, and also the pins in the switch and harness. Hooked it all back up. It changes speeds now, sometimes. But it still wont turn off. I'm gonna replace the fan speed switch with a new one. I just don't know if I should replace the wire harness in the dash or not. Any suggestions?
     
    Last edited: Apr 27, 2010
  7. fyremanpat

    fyremanpat Fyremanpat

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    thats not corrosion something got hot and melted..i had the same problem.
     
  8. nimrodcs

    nimrodcs Full Access Member

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    I know the switch and wire harness got hot and melted a bit, why, I do not know. It was rust and corrosion on the circuit board....cleaned up really good. I'm sure I can get a new switch at the parts store, but still pondering using the old harness...

    fyremanpat, did you replace your harness, or was the old one fine?
     
  9. fyremanpat

    fyremanpat Fyremanpat

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    i cleaned up the harness the best i could and re used it. I had to go it the harness and open up the connections so they made better contact.. you probably will have to ebay a whole new assembly not just a switch.
     
  10. mackysasser

    mackysasser TYF Newbie

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    Still Need Help

    Before I found this post I thought it was only the blower so I got a new one.....

    I hooked it up but didn't re-install and it won't power on......I put a voltage meter to the wires and there is juice to it when I am in low/med/high, how much though I don't know........

    I replaced the resistor next and still nothing but the voltage meter spikes...

    I had the blower tested at Napa and it works, there are no circuits out on the board either......I have not checked the switch but if I get power to the wires I assume it works.......

    I live in Wyoming, its 30 degrees and snowing right now and I have no defrost or heat......any suggestions for what to try next...I hate giving my money to a shop if I can do it???????

    THANKS! - Mack
     

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