It just adds another evaporator. But, that would improve the cooling capacity of the truck even without a bigger compressor or evaporator. Airflow thrugh the evaporator up front is pretty miserable in D2s and I think that's the bottleneck for the system.
The compressor is already somewhat oversized so performance at idle is acceptable under most conditions. It just cycles on and off as needed based on the binary pressure switch on the condenser. With the rear AC it would just cycle the compressor on a bit more often. Normal (electric) ACs can't do that because constantly cycling the compressors would kill them. They would also probably be overloaded as they reach the cutout pressures. Engine-driven compressors don't have either of those problems.
I have rear air in my Tahoe and it makes a decent difference. There is no noticeable change in the front AC but it cools down the back of the truck more quickly. You can tell the difference if you reach into the back seat. As an added plus, I can turn one of the vents around and point it at the back of my head on really hot days.
Okay, so the factory front-only system has plenty of compressor, but it's hampered by a poor condenser stuck right next to a constant-on heater core, and as-is does not cycle to maximum effect? That would mean adding the rear may not help the front too much, but it's potentially more efficient than the front; thus cooling the entire cabin more quickly and at lower temperatures? That should more quickly bring the cabin to it's lowest potential temperature with recirculation on.
I'm not sure how much the increased cycling would help without really knowing the details, but it should have
some effect, anyway.
Do you think the evaporator is large enough to get the best out of that, or does it seem it may be limiting performance a bit? I know it's probably sized for the cabin itself, but you do end up with a fair bit more refrigerant in the system with those extended lines, I would imagine.
What about the heater core being "always-on". Do you think a valve to stop it until it's needed would be useful? That's a lot of fucking heat down there, seemingly for no absolutely
required reason, and it's always come out of the vents since new unless I had the system set to cool.
I've got to get into that blend motor and clean it out as well as test the actuators. I know it's acting up a bit; probably because there was some smoking going on in there in the long past (in the middle of nowhere; the iffy blend motor is the
only evidence now, as even the inside of the dash harness connectors were cleaned once I learned my lesson... Don't smoke in cars). I can absolutely begin to tell now that the airflow out of those front vents is lower than it should be. It was never a hurricane, but it's certainly weaker than it should be at the moment.
Pulling that out may just not happen, but hopefully I can get in there enough to sort the issue. If it comes out easily enough, it might be a good time for a custom heater core just in case. Probably time for a new blower motor, as well. That's all stuff I want to handle this month, if possible. I need that summer NC heat and humidity to really test it, and I'll be adding some tint to the windows to supplement the excellent factory tint Land Rover used. Dramatically better film is available now.
I may look into a stronger fan when I get this stuff sorted as a first measure. It won't make
colder air, but it'll move it faster, potentially causing the apparent cooling affect to improve a bit just by more air passing over the driver. I really need to replace all that foam that falls apart, but that's not going to be too easy in the box.
Once I get the best I can out of what's in there and handle any leaks, I'll be able to move forward. That's why I want to stick with the factory engine cooling system for a while. If I get that working perfectly at factory temperatures for a little while, an upgrade or in-line modification will really be a quantifiable difference, rather than simply throwing parts at something and potentially missing an issue that only crops up under heightened pressure.
I still want to figure out all I can about the rear unit, though. I don't think it's a particularly straightforward installation, as I'm not sure if it can be controlled from my current panel, and I'm given to understand the wiring isn't all present, so I'd need to figure out where the harness terminates, and what's missing elsewhere.
Cheers,
Kennith