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dash vent HEAT HOW-TO

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  • dash vent HEAT HOW-TO

    FIRST- i haven't physically done this BUT, judging by the size of the A/C evaporator box and the size of a Festiva heater core, after you remove the evaporator core the heater core should fit in the evap box even if you have to slant the core a little. you might even have to blank off around the heater core if it's a little smaller than the evaporator box to get all the air to flow through it. THINGS TO TAKE INTO ACCOUNT: you will probably have to drill holes through the firewall but it's also possible that the existing hole for the refrigerant lines (whether you have A/C or not it is there already) might be able to be used or enlarged. you will have to run RETURN and SUPPLY heater hoses through it and TAP into the existing heater hoses with TEES and SHUT OFF VALVES. THIS MOD WILL ONLY WORK ON CARS WITHOUT A/C or IF YOU ARE WILLING TO DISABLE YOUR EXISTING A/C. if your car does NOT have A/C you will have to grab a few easy to remove components from one that does and you'll also need to get the heater core from you donor. feel free to suggest any improvements to this mod or even just tell me i'm full of it if you don't think it will work. to begin with, read the description of operation below and refer to the diagram of AIRFLOW in the VENT mode. they key points these inserts make is that when the MODE SELECTOR LEVER is all the way to the left, all the air comes from the OUTSIDE (or RECIRCULATED from the INSIDE), goes through the EVAPORATOR PLENUM BOX and out the 4 DASH VENTS only. this would be the MAX COOL setting if the TEMP LEVER is also all the way to the left. but what if instead of an evaporator core in there you have a HEATER CORE in it. DASH VENT HEAT! you will still use the existing heater core as usual for FLOOR heat and DEF. NOTE: in any MODE other than FACE, you'll be passing some HEATED air from the evap box heater core through your EXISTING heater core. this shouldn't be a problem. you might even get a little hotter air at the feet and defrost. it might be found to be possible to eliminate the stock heater core altogether but as i said, i haven't physically cobbled this yet. and a last NOTE. you'll have to shut the valves in the heater hoses that feed the EVAP BOX HEATER CORE in the summer. obviously this won't be for everybody, especially if you have a working A/C system but given the little time and cost it might be worth it for those driving through hard long winters. what makes it pretty easy is that the A/C components that are marked with the BLUE arrows on the parts sheet are all the A/C parts you need plus another heater core and those pieces will directly replace hose #18A586 (boxed in RED) found in the non-A/C cars. then just reattach the RECIRC/OUTSIDE air flapper (#01935) to the newly mounted evap/htr. core box. (red arrow) and if i remember correctly, NO dash disassembly should be needed.





  • #2
    I am a little lost in this whole thing. Does this show a way to get heat from the center vents? If so, how? I mean I see the red outlined boxes, but I am just not understanding what it is saying.. You know??

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    • #3
      By placing a heater core upstream of the blower, it will pull heat and push it to the dash vents
      -Zack
      Blue '93 GL Auto: White 13" 5 Point Wheels, Full LED Conversion, and an 8" Sub

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      • #4
        I don't think the evap tube holes are spaced right to fit the heater core tubes through them.

        I wish there was a way to get heat through the dash vents. Anyone try fitting the blower assembly and tubing from an Aspire?
        1991 Ford Festiva BP (Full Aspire/Rio Swap) (337k Miles) (Around 95k Engine)
        2002 Chevy Cavalier LS Sport 2.2L DOHC Ecotec (Threw a Rod)
        1998 Chevy Monte Carlo LS 3.1 V6 (225k miles) Best MPG = 28

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        • #5
          Could you just run heater hoes to the evap and have 2 heater cores?
          I know with one big hoes and one small it may not flow as well as a real heater core.
          but should give you vent heat.

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          • #6
            ^ I like where you're going with that.
            -Zack
            Blue '93 GL Auto: White 13" 5 Point Wheels, Full LED Conversion, and an 8" Sub

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            • #7
              Heater core 62mm (2.42") on center
              Last edited by bravekozak; 01-26-2014, 07:55 PM.

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              • #8
                2 heater cores would be the ticket. but I still like the F3BZ's op. hope someone can show us how to do it. I mean I never will cause I NEVER use the dash vents to heat in any car I have ever had but, this would be sweet fore people that are in need of heats.
                -Bryant

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                • #9
                  Googling "using evap core as a heater core", general gist of what I can find is that the evap is too restrictive, you wouldn't get much heat out of it.

                  Two heater cores would just make the engine take even longer to warm up on a cold day, unless you delete the one in the stock location and just run the one in the evap location.

                  I do have an extra heater core laying around, and my a/c system isn't charged yet, so I could get in there and try this out.
                  Of course come summer time I am going to pull it out and charge the a/c.
                  Last edited by TorqueEffect; 01-26-2014, 09:54 PM.
                  1991 Ford Festiva BP (Full Aspire/Rio Swap) (337k Miles) (Around 95k Engine)
                  2002 Chevy Cavalier LS Sport 2.2L DOHC Ecotec (Threw a Rod)
                  1998 Chevy Monte Carlo LS 3.1 V6 (225k miles) Best MPG = 28

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                  • #10
                    The heater core pipes will fit through the evap core holes, whether it fits in the evap box is another mystery.
                    1991 Ford Festiva BP (Full Aspire/Rio Swap) (337k Miles) (Around 95k Engine)
                    2002 Chevy Cavalier LS Sport 2.2L DOHC Ecotec (Threw a Rod)
                    1998 Chevy Monte Carlo LS 3.1 V6 (225k miles) Best MPG = 28

                    Comment


                    • #11
                      i thought this thread died outta the gate so i didn't get around to comparing the A/C evap box with a heater core to see if it was a possible fit. obviously holes and tubes aren't going to match up perfectly but that's why it's good that heater hose is pretty flexible. as an alternative to using an A/C evap box, a correctly sized sheet metal box could be used/installed somewhere along the existing OUTDOOR AIR/RECIRC AIR tube that is on all the non-A/C cars. of course the box will have to be big enough to contain and enclose the heater core. you "might" be able to just use the existing A/C evap core but you will have to adapt the evap nipples to accept heater tubing. the A/C evap core will certainly handle the pressure of the coolant system but i'm not sure if the heat transfer will be as good as using a regular heater core. there will be SOME heat. i don't necessarily agree that the car will take longer to heat up as long as you don't have the fan on high till it starts to move the temp. gauge needle. i just don't think there will be that much added coolant to make a noticible difference. bottom line and a confession is that, no. i haven't done it but, it will work. it might not be pretty, and it shouldn't take a whole lotta work. for those who are confused about the whole initial write up it boils down to this: if you can fit/enclose a heater core somewhere in or in place of tube# 18A586 shown in the red box and you can tap that core into the existing heater hoses, you will have heat out the vents.

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                      • #12
                        Will need to install some sort of inline valve though to shut off that heater core for when you don't want heat. Without some sort of cut off on the flow you will only ever have full heat. My '88 CRX and '89 Accord LXi both used a valve on the hose just before the inlet of the heater core with a cable running to the dash hvac controls to restrict or completely cut off flow to the heater core to adjust heat. That could work here as well.
                        No festiva for me ATM...

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                        • #13
                          i found a festy core i knew i had laying somewhere. it's 7"x7" and almost 2" thick. smaller than i thought and i'm pretty sure an A/C evap box is at least that big. here's another thought along the same lines. 12V electric heater plumbed into the underdash tube. instant heat. no hoses. just some wiring. here's one that might be adaptable. 8000 btu. hardwired. a little pricey but not junk. the coil/fan box is only 9"x5"x4". wish they gave the diameter of the outlets but they can't be more than about 2 1/2". i can't see why it couldn't be reconfigured to have an inlet on one end and the outlet on the other. trouble is what effect would having another fan in the system have on the stock system. could you eliminate the festiva blower wheel and just use this one? or yank the blower out of the electric one leaving just the heating coil and use just the festy fan? if i get the time and ambition maybe i'll experiment by gutting one of those cheap cig lighter plug-in heaters and fit just the heating element section in the tube to get some real world answers. next winter. http://www.12volt-travel.com/ducted-...r-p-14939.html

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                          • #14
                            Definitely would have to upgrade the alternator with one of those in there.

                            Nice find though.
                            1991 Ford Festiva BP (Full Aspire/Rio Swap) (337k Miles) (Around 95k Engine)
                            2002 Chevy Cavalier LS Sport 2.2L DOHC Ecotec (Threw a Rod)
                            1998 Chevy Monte Carlo LS 3.1 V6 (225k miles) Best MPG = 28

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                            • #15
                              So how did this work out?

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