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"Placebo" heater upgrade

Discussion in 'Early CJ-5 and CJ-6 Tech' started by colojeepguy, Dec 27, 2011.

  1. Dec 27, 2011
    colojeepguy

    colojeepguy Colorado Springs Sponsor 2019 Sponsor

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    Any ideas for improving the performance of the stock heater? I know, I know, everybody is gonna say "get a Summit heater", but my 70 CJ5 has the complete stock heater in good condition, and I really don't want to change it out. However the air it puts out is just not very warm (engine temp is 180 deg.) and I'd like to get some warmer air out of it.
     
  2. Dec 27, 2011
    Boyink

    Boyink Super Moderator Staff Member Sponsor

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    turd_polish_thumb.jpg

    ;)

    The reason everyone recommends a replacement is the OE heater is a lost cause. The difference in a Summit/Mastercraft heater is amazing.
     
  3. Dec 27, 2011
    1960willyscj5

    1960willyscj5 Well-Known Member

    Mesa, Arizona
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    You want the stock heater to work better?

    Two ways. One: you wait till summer, and two: you move to a warmer state.
    Air-cooled VW bugs came with better stock heaters.

    My '60 didn't even come with one. They were an option, like the passenger seat and other non-essential items. Passenger side windshield wipers were another option.
     
  4. Dec 27, 2011
    timgr

    timgr Jeepin' Nerd Sponsor 2019 Sponsor

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    I suspect the surface area of the heater core is just too small to bring the airbox temp up. Check that the core flows freely and the core is not plugged with debris, inside or out. There are two issues that control how much heat the heater makes, I presume. First is thermodynamics - the greater the temperature difference between the coolant and the air, the more heat will be transfered. I'd certainly run a 195F thermostat in any modern car - a 180F stat is too cold. The engine will run better at 195F, and the increase in temperature won't affect cooling efficiency unless you already have a cooling system that's right on the edge of overheating.

    Then the heat equation takes over. Assuming that the temperature of the coolant does not change much from inlet to outlet (a plausible assumption, considering the heat capacity of water compared to air; roughly 4000:1 on a volume basis), and the thermal conductivity is the same for all heater cores that are not full of sediment, then the surface area of the core has to be the main issue. You cold possibly expand the box and put a bigger core in it - that would make more surface area and transfer more heat to the air. You could also flow more iar through the core - this would make the air coming out cooler and increase the thermodynamic efficiency of the heater.

    So 1) hotter water, 2) more air, 3) larger core.
     
  5. Dec 27, 2011
    colojeepguy

    colojeepguy Colorado Springs Sponsor 2019 Sponsor

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    I'm not looking for miracles, and I don't drive it much when it's really cold, so it's not a huge deal. I was just hoping for a little more heat...
    I think Tim's idea is a good one-I might throw a 195 stat in it & see what happens.
     
  6. Dec 27, 2011
    SIDSCJ

    SIDSCJ Jeep addict

    New Haven, Vermont
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  7. Dec 27, 2011
    Patrick

    Patrick Super Moderator Staff Member Sponsor

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    So leave the stock heater in place, and just add an aftermarket unit.
     
  8. Dec 27, 2011
    PeteL

    PeteL Member Sponsor 2019 Sponsor

    Hills of NH
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    "I might throw a 195 stat in it & see what happens"

    Your milage may vary, but the 195 thermostat didn't work when I tried it for the same reason,years ago.

    Here in NH, the engine would boil over in severe cold weather, oddly enough. I believe the thermostat was not opening, since it was relatively exposed to the cold air stream and never got up to temp.

    Instead I learned to drive with the passenger window open so my breath wouldn't frost up the windshield...
     
    Last edited: Dec 27, 2011
  9. Dec 27, 2011
    nickmil

    nickmil In mothballs. Sponsor

    Happy Valley, OR
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    A warmer thermostat may help if ambient temps are not too cold. If so limiting the cold air flow through the radiator may help. The military and big rigs commonly have covers that are adjustable over the grills to limit cold airflow so they can come up to appropriate operating temps. I've had to put cardboard in front of my radiator on the past for the same reason.
    You might get some more performance from the stock heater, but regardless, it's still not a very good design. If you can get enough out of it to work the way you need, then more power to you. Best thing I did in the daughter's Jeep was remove the stock heater and put in a summit unit. Ymmv
     
  10. Dec 27, 2011
    aallison

    aallison 74 cj6, 76 cj5. Has anyone seen my screwdriver?

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    There is an upgrade using a blower motor from a Blazer for some years CJ's. I don't have any information other than that but a quick Google search should get you plenty of information. It's fairly common.
     
  11. Dec 27, 2011
    PeteL

    PeteL Member Sponsor 2019 Sponsor

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    "There is an upgrade using a blower motor from a Blazer for some years CJ's." An upgrade for the early YJ was the blower motor from a '73 Blazer. Later YJ's used a similar motor.

    How about the gasoline-fired Arctic cab heater from an M38A1? What could possibly go wrong?
     
    Last edited: Dec 27, 2011
  12. Dec 28, 2011
    jwjeep60

    jwjeep60 in process

    Sedalia Mo.
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    the blazer core is not much larger than the placebo's? the blazer motor is stronger and adaptable.
    my vote on usefulless is the lack of recirculating interior air,
    reheating interior air is still going to be warmer and will continue to raise temp each time the air recirculates.
     
  13. Dec 28, 2011
    m38willys

    m38willys Jeep Vice Sponsor

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    Had one of these in my grandfathers jeep. Don't think it was a military version as it was much smaller. It worked GREAT, and was instant heat.
     
  14. Dec 28, 2011
    colojeepguy

    colojeepguy Colorado Springs Sponsor 2019 Sponsor

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    That's a good point-the stock heater is drawing air from the grille. Plenty of fresh air, but no Jeep is airtight enough that you need to worry about getting fresh air!
     
    Rick Whitson likes this.
  15. Dec 28, 2011
    PeteL

    PeteL Member Sponsor 2019 Sponsor

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    The earlier CJ's had 'recirculation' heater only, no fresh intake. Still totally inadequate, felt like an anemic mouse breathing on your foot. Come to think of it, my YJ isn't much better.

    I never did it, but have often wondered about the effectiveness of plumbing in a section of 3/4" domestic baseboard radiator (finned tube) somewhere inside the tub, maybe below the dash...
     
  16. Dec 28, 2011
    timgr

    timgr Jeepin' Nerd Sponsor 2019 Sponsor

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    Another option would be to install a rear heater from a minivan or such under the rear seat. Then you'd get extra heat and also keep the placebo heater.
     
  17. Dec 28, 2011
    aallison

    aallison 74 cj6, 76 cj5. Has anyone seen my screwdriver?

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  18. Dec 29, 2011
    noahlon

    noahlon Old Fart

    Pine Ridge, AR
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    I have been thinking about a power invertor and 110v electric heater. Doesn't need to be toasty warm, just enough heat to be comfortable.
     
  19. Dec 29, 2011
    PeteL

    PeteL Member Sponsor 2019 Sponsor

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    "I have been thinking about a power invertor and 110v electric heater."

    If you do the math I think you would find it takes a huge amount of amps for very few BTUs. Whereas there are already enormous amounts of BTUs already being produced under the hood, and available as hot water.
     
    tarry99 likes this.
  20. Dec 29, 2011
    jwjeep60

    jwjeep60 in process

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    don't forget 60A stock alternator on the v6 at 12v
    30A on the 4cyls
    -7A ignition (hei)
    -10A headlights
    -5A running lights, turn signals and hazards
    -7.5A stock heater or -15A GM blower motor upgrade
    -15A summit or similar heater
    -8A electric radiator fan
    60a x 12v = 720watts total at rated rpm
    its easy to run out of juice at night in the cold waiting for the light to turn green...
    the 12v blower would equal 1.5 amps at 110v, sorry but 110v heater is just not practical,
    and the cost of an inverter to power it is more than a small 110 genset

    i spent $60 on new components for an 85 gmc truck HD heater; core, fan, and motor mounted in a tin case that will burn your toes, use a household 1/4 turn hot water valve to control temp. I know this setup will fit in an ammo box that would look natural in a jeep.
     
    Last edited: Dec 29, 2011

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