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Heater Control Unit

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by JROSS, Nov 29, 2001.

  1. JROSS

    JROSS 1/2 ton status

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    When the heater is on air blow out of all the vents, (not just the floor vent), and it doesn't matter what setting I have it on. Even if I set it on AC the air still comes from the same places. Is this a problem with the control unit or something else? If it is the control unit, does anyone know where I could get one? Everywhere I have tried cant get the unit for an 81 blazer with AC. Is it really that different form an 82,83, etc.

    Oh yeh, Don't know if it matters but the AC is not hooked up right now.

    Please help.

    81 Blazer C10 Silverado Package, 350, 4" lift, 35" tires
     
  2. mudhog

    mudhog THEGAME Staff Member Super Moderator

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  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Almost 100% sure you need at least one vacuum line from the engine bay to the heater control unit. IIRC, the AC trucks use a vacuum tree on the control unit to open the vent/defrost/heat. When the vacuum is cut off, you have blower motor, hot and cold, and thats it.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     
  4. Derf00

    Derf00 1/2 ton status

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    When I replaced my heater coil I found that the control arm that operates the door that controls the air flow was broken. Your problem sounds like a bads vacuum line or the control arm I described.

    Derf00
    1990 K5 Jimmy 350 Edelbrock Performer TBI, 6in BDS Lift, Dana 60 4.56, Corp 14B Detriot, 16x10 Rock Crawler, 37x12.5 SSR
     
  5. moneypit

    moneypit 1/2 ton status

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    Just had mine fixed at the dealer. There is a plastic clip that controls the door that is broken inside the heater box. This will not let it close cause it is jammed. The part was like 2 bucks at the dealer and a arm to put in. The vacuum line controls the defrosters so you do need to make sure that is hooked up as well.Now i have defrosters and control of wich vent I want. Good luck!
     

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