[o2batsea]

When I built the system for the 109 5 door, I used an off the shelf evaporator and heater core. The box I built from ABS sheet stock 1/8 thick. You use the water-thin adhesive which is basically acetone or something like that but you have to get the edges tight before applying and it more or less welds the stuff together. It cuts easy, shapes with a heat gun and is cheap. I figure if the box itself goes south I'll build it again but probably TIG it up from aluminum since I have that capability now and didn't then. I made it so that the AC evaporator (from a Range Rover) is in front of the heater core so that it drips into a "well" on the bottom and then overboard through a hole in the box. The heater core is suspended in foam so it doesn't touch the plastic but I don't think it would melt or distort it. The blowers are also poached from a Range Rover Classic AC box as they have a nice flange mount. I have the fan speed resistor mounted on top where it gets direct blower airflow. I also put the heater control valve up top and modified the air duct control to be the heater control. The control wire just slinks up through an existing hole in the bulkhead and goes to the valve. The box sits on the top of the footwell secured with a couple screws that go into rivnuts. There's a hole in the footwell and I used that but opened it up a little more and made a duct that takes the air to a modified late Series 2A heat duct thing. This I made holes in for round plastic vents that can be rotated and have little flaps to direct the air where you want it.
The 300 Tdi AC brackets are bone stock and I have a Sanden compressor on there. All the hoses, controls, fittings and ancillaries I bought from coldhose.com I have an ATCO swaging tool to crimp the ferrules onto the hose fittings. You're welcome to borrow it just pay shipping on that.
In full disclosure I haven't charged it up with refrigerant to test it due to many factors but have no reason to believe it wouldn't work.

If you buy an under-dash unit, they come with all the guts you need to fill your custom box and are fairly inexpensive. The ones coldhose carry are only like a hundred bux and have all the shizz. You just need to pull it apart and reformat.

 

[LiquidMoose]

I installed the unit shown in your link #2, https://www.amazon.com/Evaporator-Conditioning-Conditioner-Electrical-Thermostat/dp/B08MQ676F8/, except mine is cool only, no heater core. I get a 30 degree delta between outside temp and temp at the vent, better performance than the MOD unit I installed previously, but still not enough for southern AZ. I feel the unit doesn't move enough air at high speed. My 2 cents.

 

[Maximus3006]

“Persephone” is still having out of body experience but I too have been ruminating about this very issue. With her bulkhead off and now finishing the 5 speed it’ll be short order until I start this process.

I’ll keep in touch in case you need peeps to try out things as well. Easier when all apart and can sort the plumbing.
Cheers
S

 

[Sir Sam]

“Persephone” is still having out of body experience but I too have been ruminating about this very issue. With her bulkhead off and now finishing the 5 speed it’ll be short order until I start this process.

I’ll keep in touch in case you need peeps to try out things as well. Easier when all apart and can sort the plumbing.
Cheers
S

If you wish to contribute you could help with some measurements of your bulkhead, I'm sure measurements exist somewhere out there, I just haven't come across them yet. I took some the best I could laying over the fender and trying to measure around stuff bolted to mine. This would be helpful for making a new HVAC box that mates up with the bulkhead correctly. Dimensions, angle of footwell, location of stock air supply hole, those 2 threaded holes above the footwell, etc.

Something like this:

But for this:

I went ahead and ordered the Jeep evaporator I was looking at, and a dodge ram heater core. Based on the pictures I can find I think these might be about the right size, ordered the cheapest parts I could find, if they work out I can look at options that may be of better quality.

 

[Sir Sam]

Researching more I came across the company red dot which makes AC systems for OTR trucking and such. None of the systems they make seem small enough to be shoehorned into the engine bay, but I did get an idea from looking at their exploded view parts diagrams: put the blower motor right against the bulkhead where it sucks through both the heater core and evaporator, and then blows into the cabin, I think the spacing for that could be much better than having a fan as a pusher.

This means that on the opposite end of HVAC box, towards the front of the vehicle, it can just be air plenum to select between recirc and outside air.

Previously I had been thinking the fan would push air, and the HVAC box internally would be separated between the blow plenum and the heater core side.


Also searching online I found a few posts from people attempting to do the same thing as myself here, with various degrees of follow through. Some pretty good discussion came from: https://forum.aircondition.com/

In reading the relevant posts I'm solidly convinced TXV is the right way to go. However no one else shared how they were sizing or finding after market evaporators. Lots of information out there about adding AC with the assumption of an existing HVAC box.


Question for the group:
What happens if there is no flow through the heater hose connections? On my Jeep this is a problem, when cold the thermostat bypass flows through the heater core, so block that off and then the water pump is dead heading and cavitating in the housing. Now is the answer the same for a 200TDI as a TD5?

What prompts this question is the idea that the heat will not be controlled by an air mix/bypass door, that it will be controlled by coolant flow, restrict the coolant flow for less heat. Personally I prefer this method so that when you only want AC there is no hot coolant circulating right next to where you a want cold air from an evaporator. This also makes the design a little easier for the internals of the airbox.


I kinda wonder about the possibility of adding a cabin air filter to the radiator stack, might be worth looking into depending on how the space is looking. Very quickly this could get to be too deep and protrude too far into the engine bay and have an interference with the fender wing or washer bottle.

 

[o2batsea]

You don't need recirculating air. The recirculation comes into play during times of extreme heat or cold, in which the outside air overwhelms the ability of the system to heat or cool. It calls for a pretty big return air duct back to the air intake, so you have to decide if there is room for it. On the 2A, it would mean cutting a rather sizable hole in the footwell so I didn't. If I had gone forward, I would have taken the air from the outside upper panel of the footwell box, and fabbed up a duct between it and the wing to the intake and made a flapper box. Access to the bolts that hold the wing to the bulkhead was gonna be a problem and I couldn't really come up with anything better plan-wise so, yeah.
The blower being downstream of the evap and heater core isn't really a thing. You'll have the same airflow either way. I think having the blower external is better for access and maintenance. It may be slightly quieter outside. To have a blower effective enough will take up a significant amount of footwell space.
Range Rover Classic and Defender had two small axial fans in the footwell blowing across the AC evaporator. There is a switch on the controls that you select either heat or cool and it switches between the outside heater fan and the inside cooling fan(s). If you plan to split up the system so the evaporator is in the footwell and the heater core outside, then this will be a consideration. It does eliminate the recirculation issue for the AC. I think it's not needed for heat anyway. Having the evaporator inside means plumbing the water overboard somehow. More holes.
If there is no flow through the heater core, it'll assume ambient air temp although it might absorb a small amount of engine heat. With the heater valve shut, the plumbing circuit is closed, so the hose coming from the engine might get warm but not enough to amount to anything.
I will again recommend the evaporator from a Range Rover Classic. It's the right size for the truck, easy to source for cheap, and they don't go bad. The in/out are of the clamp-down o-ring type directly on the expansion valve (metric) so the fittings are standard-issue. If you'd like, I will find you one.

 

[Sir Sam]

You don't need recirculating air. The recirculation comes into play during times of extreme heat

Yes exactly. Even in my other vehicles I frequently use recirc air in the summer, for me a proper AC system needs recirc air for max cooling in the summer.

It calls for a pretty big return air duct back to the air intake, so you have to decide if there is room for it. On the 2A, it would mean cutting a rather sizable hole in the footwell so I didn't.

Yes, right now my thought is that the recirc air hole will require a large hole to be cut in the footwell, similar to what the mod unit uses for its only air source. If someone didnt want recirc air they could just use the outside only air and not make the recirc air hole.

The blower being downstream of the evap and heater core isn't really a thing. You'll have the same airflow either way. I think having the blower external is better for access and maintenance. It may be slightly quieter outside. To have a blower effective enough will take up a significant amount of footwell space.

I'm still talking about the fan being in the HVAC box in the engine bay with heater and evap, just placing the fan as a puller instead of a pusher for packaging. Many thoughts are still nascent and without good dimensions my internal spatial reasoning isn't very confident on fitment yet. I've attached a few rough sketches to help illustrate my thinking so far.

So far I havent found a twin centrifugal fan that I think will work, all of them appear to be a fair bit wider than we can deal with given the width of the existing heater box and bulkhead.

I will again recommend the evaporator from a Range Rover Classic. It's the right size for the truck, easy to source for cheap, and they don't go bad. The in/out are of the clamp-down o-ring type directly on the expansion valve (metric) so the fittings are standard-issue. If you'd like, I will find you one.

If you have a RR classic evap around the dimensions and some pictures at this point would be handy, the more accurate/detailed the better at some point as I try to hone in the CAD. I'm not opposed to using land rover parts, I was just looking for what I could find and what would be readily available in the US for an extended time period with multiple options. Mass produced appliances vehicles fit the ticket there.

From what I'm finding of pictures on the web, the RR classic evap doesnt seem like the plumbing is easy to use, but without the expansion valve and piping maybe I am missing something.

 

[J!m]

You could potentially hide the recirc inlet behind the fuse panel...

 

[Red90]

Fan should be pushing through the heat exchangers not pulling for various reasons.

Recirc flap moves from closing the recirc port to closing the fresh air inlet port. Use the stock fan speed lever. Make sure fresh air is ducted from a safe location.

 

[mockingbird30]

I'm in the same boat working on modifying one of my RHD heaters for my LHD Defender and looking for a better heater core. Rover left tons of unused room in there and the outlet hole is tiny. I'm interested to see what you find and might try some of your ideas myself. New heater assemblies are stupid expensive for what you get.

I find it amusing my old Kodiak Series heater would roast you out of there and the Defender heater will barely warm up your kneecaps . I live somewhere between Ouray and Grand Junction. Thank God we don't have to contend with -40. it rarely even gets to 0 deg. It does get hotter then Hell though.

 

[Red90]

New heater assemblies are stupid expensive for what you get.

There are lot of options for low cost aftermarket heater assemblies. You just need to build an adapter to fit the bulkhead.

 

[Red90]

This one is a nice size. There are other options around, so worth doing some research. Summit Racing SUM-991102-1 Summit Racing™ Automotive Heaters | Summit Racing

 

[Sir Sam]

You could potentially hide the recirc inlet behind the fuse panel...

Thats an idea I had not considered! Still requires cutting the bulkhead for recirc but I see no way around that if you want recirc air. Downside I see with that is it would require fabbing some ductwork. ABS 3d printed duct could work nice......but thats a different level of fabrication.

Ive been keeping this in my mind as sheet metal and bend. That way someone could always print paper templates, trace it to metal, cut by hand, and bend by hand, if they didnt have access to the same level of fab tools. Part of the goal here is to make this easily repeatable for others in the future(including myself). Not everyone has a 3D printer, but cutting sheet metal to size and finding a straight end to hand bend it on is doable. Likewise cutting ABS sheet and heating to bend, and using acetone to glue ABS together, is another decent option.

And....I have a proverbial hammer(CNC plasma table and finger brake) so everything starts to look like a proverbial nail to me(sheet metal and bend).

Fan should be pushing through the heat exchangers not pulling for various reasons.

I have no real horse in the race between the two other than the packaging seemed a little better. The differences I see are:

Push: heated air does not flow over fan motor, maybe longer motor life.
Pull: potentially might be after a filter so dust buildup on motor may not occur as much if thats really a consideration.

Any other reasons you can think of? Just trying to get all considerations on the table to justify an engineering decision.

Recirc flap moves from closing the recirc port to closing the fresh air inlet port. Use the stock fan speed lever. Make sure fresh air is ducted from a safe location.

Sounds like your following my intention from my 3rd image flap location above. I like the idea of using the fan level to move the door, simply and effective as long as we can get the cable to route and work there. I hadn't been thinking along those lines since the first system I have will be using a MOD puma dash, so I was looking at vacuum and electric blend door actuators.

Fan control is easy with a rotary switch and resistor pack, and some blowers are built to be multiple speed, and there is also the options of PWM fan controller for infinite adjustment. All are viable depending on how much effort and complexity someone wants for the fan control.

I'm in the same boat working on modifying one of my RHD heaters for my LHD Defender and looking for a better heater core. Rover left tons of unused room in there and the outlet hole is tiny. I'm interested to see what you find and might try some of your ideas myself. New heater assemblies are stupid expensive for what you get.

I find it amusing my old Kodiak Series heater would roast you out of there and the Defender heater will barely warm up your kneecaps . I live somewhere between Ouray and Grand Junction. Thank God we don't have to contend with -40. it rarely even gets to 0 deg. It does get hotter then Hell though.

I do vividly recall driving back from Ouray through GJ when it was in the upper 90s outside. We aren't southern AZ hot, but we do get hot.

For just heat alone and not AC I think the upgraded alisport heater core seems like a decent option thats not too difficult, along with the other typical heater box refurb/mods. The standalone heaters custom mounted to the bulkhead are also good options. Wanting AC is a complication for those thats opened up my considerations.

This one is a nice size. There are other options around, so worth doing some research. Summit Racing SUM-991102-1 Summit Racing™ Automotive Heaters | Summit Racing

That is a nice size, much narrower than others I have come across, and the depth doesn't automatically exclude it either, thanks for the link. Its worth considering for a starting point and then repacking or packaging further.

 

[J!m]

Take the left-hand controls (two levers) and make them work on the right side as well. One repurposed for the recirc flapper.

 

[Sir Sam]

This one is a nice size. There are other options around, so worth doing some research. Summit Racing SUM-991102-1 Summit Racing™ Automotive Heaters | Summit Racing

Right now this setup is basically right at the interference with my washer fluid bottle on my 200tdi, I know later Defs have a different location bottle that would gain some access, but its into not fitting territory.....and this is without an AC evaporator yet. Maybe a wider but not tall and not too deep AC evaporator could be after the heater, but if I have to move it all back to put an evaporator in the stack it starts to become a problem.

 

[WreckITFrank]

Are you modeling the design of the MOD AC box?

 

[Sir Sam]

Are you modeling the design of the MOD AC box?

No. But our problem statement is basically the same, "how can I improve heating and more importantly add AC to a defender by the most minimally invasive and simplest method possible" or something like that. We could back it up a bit and talk about different options that would solve that problem, Ive narrowed in on replacing the HVAC box with a new design. Functionally this would end up similar to the MOD hvac box, but I am in no way copying their design, this is greenfield for me. I'm looking for my own solution as a means of cost saving for my 2 defenders.

 

[Sir Sam]

Jeep Evap and dodge heater core arrive today. The Jeep Evap looks beefy, its bigger than i remember, and the dodge heater core...looks small.

Anyways. some pics:

 

[Sir Sam]

 

[Sir Sam]

So I went out and measured where the top of the box comes to in the factory form, I think I'm going to need to use all the height I can muster to make this evap fit right up to the hood line. I can also see where clearance is starting to become an issue left to right with respect to the turbo on my 200TDI for a RHD airbox.

Looking at an updated box that goes as high as I dare take it....it could work, but space for a blower is getting tight:

I played a bit with ideas of angling the stack a bit to see how that might help:

And with the first Spal fan I was considering I realized its just too damm big, Then I looked at side mount options like stock: