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How do I remove heater core from mix box?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by DieselSub, Jan 15, 2006.

  1. DieselSub

    DieselSub Registered Member

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    I'm replacing the heater core on my 85 K20 diesel, equipped with A/C.

    I followed the FSM instructions for removing my heater core - and I have the mixing box out of the truck but can't figure out how to remove the heater core from it. I've read the tech post on this board and it says:

    "Once out you will see the heater core is held in place with a metal ring that also retains the blend door."

    From what I can tell, the box is two parts that clam shell together. I've removed all the screws, but it looks like the hinge pin for the blend door is keeping it all together. I can't figure out how to remove the hinge pin and don't see a metal retaining ring.

    Can someone help? What did I miss. And yes, I'm sure the answer is going to be dead simple :doah:
     
  2. rcamacho

    rcamacho 1/2 ton status

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    There's two doors from what I can recall. One of the doors requires you to pull the shaft out in order to separate the box.
     
  3. rick88blaze

    rick88blaze 1/2 ton status

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    Check out this article in the Technical articles link on the homepage. I used it and changed mine out with no major problems. :D

    Rick
     
  4. DieselSub

    DieselSub Registered Member

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    Yep - I read that plus I have the FSM. I'm stuck on the very last step - how to separate the heater box halves. There's a hinge pin holding a flap and people have mentioned a retaining ring *somewhere* inside but I can't for the life of me find it.

    I'm sure I have to pry something a little bit apart and then the little bugger will be obvious. I just don't want to pry the wrong place and break the plastic :eek1:

    Is the ring on the lever arm end, or the "pointy" other end?

    Thanks,

    Mike
     
    Last edited: Jan 16, 2006
  5. rick88blaze

    rick88blaze 1/2 ton status

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    I remember a screw that I had to take out that was in between the 2 halves. It was a pain, but using a magnetic screwdriver really helps. Plus you have to pull the rod that goes through the flap that directs the air. Mine just pulled out, it didn't have a retaining ring or anything. It just kind of snapped into place.

    Rick
     
  6. DieselSub

    DieselSub Registered Member

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    Fixed!

    Thanks to everyone who posted advice. Here's what I had to do:

    1) Remove all the visible screws
    2) Remove two screws hidden under the foam gasket
    3) Remove the hinge pin for the mixer flap
    3a) The hinge pin has no retaining clips - it sits in the car in a vertical position and can't fall upwards :)
    3b) My pin was seized in place - I used a flat head screw driver on the end opposite the arm where the flat of the pin presents a small slot. This allowed me to wedge the two apart and loosen the whole thing up
    3c) Once loose, the hinge pin pulls out of the body of the box from the hinge pin arm side
    4) There is a screw holding the middle vacuum actuator to another flap. With the box halves slightly separated you can slide a small nut driver in there and loosen it up. Its a good idea to etch a small mark on one of the arms so you can reassemble it in the same position.

    And that's it. Really simple once you know how things go together :)
     
  7. rick88blaze

    rick88blaze 1/2 ton status

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    I'm glad to hear you were able to get it figured out. I was sketchy about doing mine, but it wasn't near as bad as I thought it would be. :D

    Rick
     

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