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blower fan quit blowing, what to check

Discussion in 'The Garage' started by ciffer, Dec 9, 2009.

  1. ciffer

    ciffer 1/2 ton status

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    the blower fan on the suburban quit working recently. i had switched the hvac control to "off" for the first time in long time (trying to listen to a far away AM station). when i turned the heater back on the fan wouldn't blow.

    the slider hasn't really changed anything for the last two years, aside from making a vacuum hiss in anything except one position, i think "bi-level". now the fan won't turn on, i still get a little heat out of the vents, but it is not blowing.

    what do i do for trouble shooting this?
     
  2. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    Direct power the blower to see that it still works then have to go from there if it does. It could be the switch or the relay or anything inbetween.
     
  3. lectric80

    lectric80 3/4 ton status

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    As Scott said, check the ground at the blower motor first, then apply direct power to the motor from the battery. If it doesn't come right on, try tapping the motor housing a bit to see if the comm has a bad spot just like on a starter. If nothing in this brings the fan on then you know the motor is bad.

    If it works move on to the switch, and test it by jumping the power from one terminal to the next, if that works then hook the switch back up and see if the power is being redirected by the switch. If not replace the switch.

    One thing to remember, the fan blows air regardless of the controls being in the off position, this forces fresh air in at all times. If the fan is not blowing at all, it is most likely either a bad ground, bad power wire, blown fuse, or a bad motor, not necessarily in that order. The fan runs always when the key is in the on position, regardless of the position of the blower switch or the controls.
     
  4. 4xcrazy

    4xcrazy 3/4 ton status

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    you have an interesting setup if your does this, my '89 blower motor DOES shut completely off when the heat/ac selector lever is set to the "OFF" position.

    in any other position, yes, it's always on.
     
  5. lectric80

    lectric80 3/4 ton status

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    Actually it isn't unique to my Blazer, it is every vehicle built after the 1970's, as it was federally mandated. Both my 94 Astro and my 96 Safari do it, as has every vehicle I have ever owned exept my 74 VW Bug (it didn't have a fan:grin:). It is very slow speed, but it is always on.
     
  6. djtejas

    djtejas 1/2 ton status

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    My fan turns off when the heat/ac lever is turned to off on my 83 Blazer...
     
  7. diesel4me

    diesel4me 1 ton status Premium Member

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    Models with AC will shut off the blower if the temp control/AC slider is in the "OFF" position,but all that dont have A/C ,the blower runs at low speed even with the speed switch in the off position,as stated already...

    You might have a fried blower motor resistor too,if the motor works with 12V applied directly,and the switches seem to check out OK--its usually located next to the blower motor under the hood,has a few wires and a plug going to it,and two screws mounting it to the heater box--the resistor coils are on the inside ,so the air fro the fan can blow on them and keep them cool..
     
  8. djtejas

    djtejas 1/2 ton status

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    From my experience with my vehicles, it's usually just the blower motor and it is easy to replace.

    since it's in an easy location to get to, it's easy to test it with a multimeter. just check the voltage at the power wire going into the motor with the control in the AC, Vent, Heat, or Defrost postions. depending on which position the fan speed switch is in, the voltage will be different...4 speeds...if there is voltage present, the motor is the problem.

    like someone else stated before, it's easy to test without a meter too...just run power directly from the battery with some wires.
     
  9. diesel4me

    diesel4me 1 ton status Premium Member

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    Guess I have been lucky,most of my "dead" blower motors popped the fuse because a mouse got decapitated in the blower fan,or a pencil or something fell down the defroster duct and jammed it up..I had to replace 2 resistors on my other trucks,but they litterally rusted away,then burnt up,but I still had "HI" speed !..
    I hated the horrible screeching noise my blower motors made in frigid weather in the "off" position when they were cold,it made my skin crawl and it'll startle you BAD ,so I snipped off the wire that let it run "continuously"..
     
  10. ciffer

    ciffer 1/2 ton status

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    i didn't even think to check the fuse. i'll do that tonight when i get home, testing the motor will have to wait until the weekend, currently -7F here.
     

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