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A/C Blower fan motor

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by ftn96, Aug 15, 2001.

  1. ftn96

    ftn96 1/2 ton status

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    I have replaced the fan motor and the switch in the cab at the control panel. The fan still doesn't work. Is the voltage resistor the only other thing I nede to replace to get this biotch to work? The fuse is good too.
    90 model FYI

    In search for the sound of frying bacon!! [​IMG]
    3/4 in progress[​IMG]
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  2. POWERMAD

    POWERMAD 1/2 ton status

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    On the ones that I have seen go bad all they will do is work on high.
    The K5's blower went wacky last winter and I found that it was the ground.
    If you have a test light check to see if there is power to the resistor from the switch.
    And from the resistor to the fan.

    my truck's not dirty, it's earth tone paint
     
  3. ftn96

    ftn96 1/2 ton status

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    Mine has done the exact opposite, it first stopped working on high, so I left it on the next one down adn it worked for a while. Then it just quit all together. Then I could jiggle it a bit and then it would work for about 10 minutes then quit again.


    In search for the sound of frying bacon!! [​IMG]
    3/4 in progress[​IMG]
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  4. POWERMAD

    POWERMAD 1/2 ton status

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    It sounds like the resistor has gone bad.


    my truck's not dirty, it's earth tone paint
     
  5. ftn96

    ftn96 1/2 ton status

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    Well, I hope so. I ordered one from LMC last night. It should be here in a couple o days. We'll see what we'll see.
    It really sucked to get my freon recharged yesterday adn replaced a valve stim to fix the leak and the damn motor wouldn't kick on. So I have to go back to dudes house to re-check the freon level once I get the motor running. [​IMG]

    In search for the sound of frying bacon!! [​IMG]
    3/4 in progress[​IMG]
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  6. HarryH3

    HarryH3 1 ton status Author

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    That's actually the classic symptom of a blower motor relay failure. On the lower speeds, power is routed through one side of the relay contacts and through the resistors. When you switch to high, power is routed directly from the battery, through the other side of the relay contacts. None of the resistors are in the circuit when the switch is set to high. Over time the swtiched part of the relay weakens and will start working only on high or only on the lower speeds, but only occasionally will it work on both. Eventually it gets stuck in the open position so no power is going to the motor at all.

    Trace the wire from the motor and it will lead you to the relay. It's usually mounted on the fiber box that contains the a/c evaporator. $10 or so and things should work as good as new.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
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  7. ftn96

    ftn96 1/2 ton status

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    HAIR-E, thats exactly the part that I ordered! I tried unpluging it and re-pluging it to no avail. So since you da man, I'll take yo word that the new one will fix the SOB!!!

    In search for the sound of frying bacon!! [​IMG]
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  8. HarryH3

    HarryH3 1 ton status Author

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    Why did ya have to order one? Any parts store keeps those in stock. They're a pretty high failure rate item on GM cars and trucks. [​IMG] I've probably had to replace 10 of them over the years. Of course, most of that time I lived in the south, where the a/c blower was pretty much set on high 90% of the time. [​IMG] That causes the relay to run pretty hot since it's got 25 amps or so of current running though it on high. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
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  9. ftn96

    ftn96 1/2 ton status

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    I thought I remembered someone saying they were hard to find. So I ordered it. I guess I thought wrong. [​IMG]

    In search for the sound of frying bacon!! [​IMG]
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  10. jcg

    jcg 1/2 ton status

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    I had the same problem. The fan wouldn't work on high so I replaced the relay but it still won't work. Got any ideas?? I've checked all the wiring and it looks good.

    Joe
    RIT Mini-Baja www.rit.edu/~bajawww
    Team Mudnuts www.mudnuts.org
     
  11. HarryH3

    HarryH3 1 ton status Author

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    Get out the voltmeter and see if there's a full 12 volts to the motor when the switch is set to high. I've had one GM where the brushes wore out in the motor and it wouldn't run on high, then it got progressively worse. A new fan motor fixed that one. But check that voltage before you buy a $35 motor. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
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  12. ftn96

    ftn96 1/2 ton status

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    Well, swapped out the voltage "resistor" no dice.
    Found that the relay was the problemo. Jacked with it adn sanded the contacts (well chad did) and it works like a champ now.
    Thanks everyone![​IMG]

    Learning to fry bacon!! [​IMG]
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  13. HarryH3

    HarryH3 1 ton status Author

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    If you'd have asked before you ordered you could have spent the money on a relay instead of the resistor pack. [​IMG] [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
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  14. ftn96

    ftn96 1/2 ton status

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    Yeah, but now I have a spare[​IMG]

    Just say no to crack(s)
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