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Heater fan switch

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by balazerjake86, Nov 25, 2002.

  1. balazerjake86

    balazerjake86 Registered Member

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    My Blazer has a problem with the heater fan selector switch. I bought a new one and that still did not work the fan speeed is the same. I also bought a new relay the one that is connected inside the engine compartment near the blower motor. What is going on here? it will turn on and of but the fan is going the same speed
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    There is a resistor that changes the fan speed...low speed goes through the highest resistance, high speed bypasses the resistor etc. Maybe someone bypassed the resistor? What speed does the fan go?

    Rene
     
  3. balazerjake86

    balazerjake86 Registered Member

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    the fan goes like if you just directly connect the blower motor to the batt. so i guess almost if not full speed. wher are these resistors?thanks
     
  4. Stoopalini

    Stoopalini 1/2 ton status

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    If I remember right, the resistors are mounted right on or near the blower motor; under the hood on the passenger's side.

    Also, I think they are pretty big resistors and don't look like the usual cylinder type resistors. They are more like springs that limit voltage.

    When the fan switch is on high, a relay should trigger and route a full 12v right to the fan. When the switch is on any other setting, the relay should switch off and the current gets routed through one of the resistors.

    You could run a hot wire from the battery to each resistor (spring) and see if they are bad or not?

    Thomas.
     
  5. balazerjake86

    balazerjake86 Registered Member

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    thanks alot for your help. i just want to clarify one thing:
    we are talking about resistors and not the actual relay right? i will look for them when i get a chance. also whenver i replaced te relay i cannot turn on the heater motor but the switch works that controls climate and a/c heat vent etc. right now i have in connected to a toggle switch but was wanting to get rid of it becuase it sucks having only one fan speed. also How doi check these resistors can i hook a wire to the resistor and the blower motor and then touch the differnt points. thanks again for all help
     
  6. Stoopalini

    Stoopalini 1/2 ton status

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    Yea, I'm talking about the resistors, not the relay. The relay is only used when you switch the fan on to full high.

    If you don't get any fan at all with the factory switch, and you are using a toggle to turn it on high, then the 12v POS lead to the relay/resistor is probably shot. Do you have a meter? If you find the resistor box, there should be a harness plugged into it. One of those wires should be hot as long as the ignition is on. If it's not, then that's your problem.

    Thomas.

    BTW: Just checking, but did you check the fuses first?
     
  7. balazerjake86

    balazerjake86 Registered Member

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    Thanks for all of your help. That sounds really logical though I am not as electrically smart as i like to be. I had no idea that the relay only works when the fan is on high. i guess you learn something everyday. it will probably be a week or so before i can look at it cause i am like 300 miles away from my blazer but will tell you if that was the case. when i bought the blazer it was all rigged up and i was trying to get it to work right so i bouhgt a new relay and it didnt work so i hooked up better than what it was. How in the Hell do you burn that lead up anyway? thanks again /forums/images/graemlins/ears.gif
    also if that one lead is burnt up can that short out other things innthe truck also like the intstrument cluster?
     

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