aftermarket heat an A/C with factory dash and center console evaporator? (1 Viewer)

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My '81 BJ has the factory center console rear heater as well as the in-dash heater. Both have coolant lines running to them to bring engine heat to the evaporators. I was wondering if it would be possible to use the factory evaporators with an aftermarket A/C unit. I'm hoping there is a kit that goes in the engine bay that takes the hot coolant lines from the engine and cold coolant lines from the compressor and does heat exchanging with two coolant lines that go into the cabin. Then I can hook the two cabin coolant lines to the factory evaporators and get either hot or cold air from them.

Is there an aftermarket solution for heat and A/C with factory evaporators?
 
If they were evaporators instead of simply a heater coil maybe. A/C evaporators would have a metering devise that restrict the flow of liquid refrigerant so it goes to a gas and absorbs heat. It is also has much higher pressure.
 
You can not use the same cores.
At first the two media’s are completely different and can not be mixed.
The heating is done by letteng hot coolant from the engine flow through a small radiator.
By blowing air through it the air heats up and the coolanr cools down.
It requires a constant flow with litlle resistance, just from the heater valve to control the amount of heat.
An AC works in a completely different way. It uses the principle of a flued converting to gas which absorbes the heat from its surrounding. An evaporator has a restricted flow at its entrance, high pressure flued reaches the restriction after which it gets a lot of room to expand. This will only work if small ammounts of flued are released in the evaporator at a time.
An AC system is completely closed and if it was combined with engine coolanr it would destroy the AC compressor in seconds.
 
You may be able to find a vendor to make you an evaporator for strictly A/C or you can go this rout...

Old Air Hurricane
 
I should probably add the 74+ heater that vent on the top is only air from blower. Only air from the bottom has passed thru the heater core. since cool air is heavier then warm air. If you look at vehicles with rear air the vents are in the ceiling. And the heater core with water/antifreeze are on the floor. Paying someone to make custom evaporators to keep the stock look would be a waste of money. Figure if your willing to spend money for custom evaporators you need the A/C to work.
 
Vegas I like your thinking. By putting a engine compartment water over evaporator one could then run the water through the stock heater cores for cooling. Would need to add a circulation pump to run the water through the cores and a valve to switch between heat and cold. I have been planning to add air to my 79 but didn't want the aftermarket look . Think I will have to ponder this idea some more.
 
Vegas I like your thinking. By putting a engine compartment water over evaporator one could then run the water through the stock heater cores for cooling. Would need to add a circulation pump to run the water through the cores and a valve to switch between heat and cold. I have been planning to add air to my 79 but didn't want the aftermarket look . Think I will have to ponder this idea some more.

If you want to keep the factory start looking for the factory A/C. Heater were designed to blow heated air and the floor and let the heated air rise or against the windshield to defrost or defog. 78 and later had the optional side glass defroster vents. Blowing cold air out the heater would only help with heat coming in thru the floor and side defroster vents switched to blow inward would not do much. Going thru the cost of adding a heat exchanger think you would be disappointed in the results.
 
Vegas I like your thinking. By putting a engine compartment water over evaporator one could then run the water through the stock heater cores for cooling. Would need to add a circulation pump to run the water through the cores and a valve to switch between heat and cold. I have been planning to add air to my 79 but didn't want the aftermarket look . Think I will have to ponder this idea some more.

That's what I was thinking. I have no idea how effective/efficient it would be, but in theory the coolant in the lines to the heat exchangers could be heated or cooled. Yes it would need a circulation pump and design a hot/cold heat exchanger between the coolant lines and the hot/cold in the engine bay.
 
"If you want to keep the factory start looking for the factory A/C. Heater were designed to blow heated air and the floor and let the heated air rise or against the windshield to defrost or defog. 78 and later had the optional side glass defroster vents. Blowing cold air out the heater would only help with heat coming in thru the floor and side defroster vents switched to blow inward would not do much. Going thru the cost of adding a heat exchanger think you would be disappointed in the results."


Living in the Past I agree that cool air delivery would not be the best as I know that I like the air conditioning vents pointed to blow in my face and also my 79's side window defrosters are mainly a joke. Thinking defrost would perhaps be the best but don't know. But no new holes in the firewall with just a few wires added to the existing wire loom sounds appealing and easily removed if in practice it failed to preform.
 
That's what I was thinking. I have no idea how effective/efficient it would be, but in theory the coolant in the lines to the heat exchangers could be heated or cooled. Yes it would need a circulation pump and design a hot/cold heat exchanger between the coolant lines and the hot/cold in the engine bay.

vegas I am thinking that I will try this when I get time. May find some problem that I haven't thought of yet like not finding the right circulation pump or valve to switch hot/cold but not at all afraid to make the water over evaporator. If you do this first please post so I may learn what you did and if it works.
 
My problem is that I'm not sure I want to spend $1000 on a vintage air A/C unit to use on an experiment like this. The hot side is the easiest. Use the existing engine coolant circulation system that then run the in-cabin coolant and the engine coolant through a reverse flow chiller/heat exchanger like what people use in wort chillers for brewing. There's lots of ways to fabricate one. It's the cold side the I'm most concerned with. I guess you could do a similar thing with the in-cabin coolant flowing in a spiral around the cold side of the A/C evaporator. Then the only thing left to figure out would be the valve system to either allow hot engine coolant flow through the hot side or turn on the A/C unit to cool down the cold side but not both at the same time.
 
Then the only thing left to figure out would be the valve system to either allow hot engine coolant flow through the hot side or turn on the A/C unit to cool down the cold side.

Not really, A/C moves more air than the heater blower in a FJ40. You also need to figure a thermostat to cycle the compressor. I worked for a mechanical contractor where we made a few one off small process chillers. One thing we found out was we needed a larger volume of water to prevent short cycling the compress. With direct expansion, refrigerant to air your using the whole cabin as your heat source. With the chiller it's the temperature and volume of water. Small volume of water and poor heat exchange due to low air volume you will short cycle the compressor or worse risk getting liquid refrigerant back to the compressor. Not sure how efficient the heater coils in a FJ40 or the lower volume of air will effect the heat exchange.
 

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