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A/C Firewall box swap

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by doc70sub, Oct 19, 2002.

  1. doc70sub

    doc70sub 1/2 ton status

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    Is it possible to swap out the A/C box to a regular, heater-only box on the firewall? I'm pulling the A/C off of my '79 K-5, but want to still have a heater w/o the big-a$$ box hanging there in the way.

    Anyone interested in the A/C compressor, brackets (400 SB) firewall box, etc.? I'll have it on the shop floor soon enough! /forums/images/graemlins/rotfl.gif

    Thanks!
    Doc /forums/images/graemlins/k5.gif
     
  2. HarryH3

    HarryH3 1 ton status Author

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    I think that the firewall is different between the two. You'll need to weld in a patch as the hole in the firewall is much smaller in the "no a/c" version.
     
  3. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    You'll need both the box on the outside in the engine compartment,it houses the blower motor, and the box on the inside which houses the heater core and baffles. You will also need the heater controls. I scored all three pieces at a junkard for $30. You cannot simply swap on the outer box, as it does not match the airflow holes on the inner box.
    There is a difference in the firewalls, you'll need a patch to cover the AC hole, its about 8x12, and the heater hole, if I remember , will need to be cut. The other differences are the kickpanel vents are vacuum controlled on AC models, which if you swap the heater controls, will no longer work, but you can buy the pull lever for a few cents from LMC or Chevy duty, remove the knockout and your set. You'll want the ventes operational in the summer time, they are a BIG help. Also, there is a kickpanelvent on the driver side, just like the passenger for non/ac equipped trucks. It's nice to have, but not neccessary. YOu can also buy this vent from LMC or ChevyDuty, you'll have to cut the hole.
    Make sure to remove that vacuum line/s (depending on year) going into your cab and plug that source, you don't want your truck to run like crap because you forgot a vacuum line There's an vacuum operated air baffle on the outside, beneath the air intake grille for AC trucks, at least on the '70's models. You'll want to remove that.
    While the blower box is removed, take a few extra mintues to clean out the cavern going down the side of the Front Body hinge piller.It's the reason rust forms there at the bottom of the rear front fenders, it's a sealed area. It's easy to get at while the blower box is removed and helps if the kickpanel vent is removed. I drilled a nice big hole in mine, then put a rubber plug in it for a cleanout. You don't want to leave a hole, it will make all kinds of howling noises and reduce your airflow into the cab.

    BlazerMan
     
  4. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    Oh Yeah, then you can remove all the under dash vents and ducts that come out above the glove box, ash/tray above the radio and next to the headlight switch. You'll need to replace the Dash Pad trim with a non/ac piece of trim and the Instrument panel bezel.
    You will also need to move the heater core inlet holes in the firewall.

    What I did, when I got the pieces for the non/ac from the junk yard, I took a piece of cardboard big enough to cover that area of the firewall, then cut out all the neccessary openings. That was a perfect template for transfering those opening to my firewall...
    The whole thing sound like a lot, but it's really not a big deal. About a half day job, plus the time at the junkyard...

    BlazerMan
     
  5. Michael

    Michael 1/2 ton status

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    I agree with 73....I did mine and it was no big deal. I welded in patch panels, but they could be rivited and sealed if ya don't have access to a welder. Here is a shot of the outside.
    [​IMG]
    The A/C dryer is for an aftermarket setup.
     
  6. doc70sub

    doc70sub 1/2 ton status

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    Thanks guys!!
    D.
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Also, if you don't get the heavy duty heater box (optional, fairly uncommon) you might be disappointed when it comes time to run the heater and defrost. The AC setup uses a much more powerful fan than the non AC, non HD setups.
     
  8. doc70sub

    doc70sub 1/2 ton status

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    I appreciate all of the info guys! As far as performance of the heater goes, I'm whacking the top off & probably asking for some cold rides anyway!! /forums/images/graemlins/rotfl.gif
    Doc
     

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