Heater issue.....pita

Discussion in 'Chevy C/K Truck Forum' started by robs1992chevywt, Jan 20, 2012.

  1. outalne94z71

    outalne94z71 Member

    there is no relay for speeds, the switch changes where the power goes through that resister pack in the top of the heater box, that it what controls speed, usually the slower speeds fail and high only works as its full 12v
     
  2. Scott_Anderson

    Scott_Anderson Rockstar 100 Posts

    I think you will probably have to trace it the old fasioned way.
    Take that wire bundle that plugs onto the resistor pac(on the top of the duct in your pic) and follow it to the relay.
    I found a general gm circuit schematic of how the blower circuit works, but not specific to your exact vehicle.
    Here's the link:http://www.autoshop101.com/forms/gmprac.pdf
    What u will be looking for is on pages 72-75. It's basically the same page repeated 4 times. select the page and rt click and select rotate clockwise so you can read it easier.

    For the low speeds the current goes thru the resistor pac, then thru the normally closed contact of the blower relay when the relay is DE-energised.
    When you turn on the high speed the relay is then Energised and sends direct 12V from a different fused circuit to the blower.
    You will have 2 different fuses that control power for the blower motor. 1 that is only energised when ign is on(for low speeds, and to turn on the relay), and one that is on all the time(only switched by the relay for blower high speed).

    Another option to try and find the relay, be very quiet, and listen for the relay clicking when you turn the high fan on/off.
     
  3. DanPruski

    DanPruski Member

    okay, just looked it up, look under the hood, passenger side of the firewall, theres a black plastic cover (Power Distribution Center) its labeled on the cover as BLOWER, check that, it may be a fuse, relay, or fusable link. thats where i found online to check atleast.
     
  4. robs1992chevywt

    robs1992chevywt New Member

    Dan, i checked the cover and the only things labeled are. ground Fuel pump relay fuse junction block fuel pump relay optional relay ground
    there is no "Blower" on my cover....my truck is a pita
     

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