Rooftop AC unit

What you want to do is open the dash panel with the heater control in it and look around the harness the wires to it come from. The wires for a/c control may already be in that harness. If you find them there, you’ll probably find the wire for the compressor clutch hanging out of an engine harness somewhere near where the compressor would mount on the engine. If you find those wire ends then the truck is probably wired for a/c already and you only need to plug components in. If you find a donor truck with the a/c intact you’d get the condenser and evaporator and the hoses, the heater-a/c control out of the dash and the compressor brackets and pulleys too if the donor has a Cummins. I don’t know if the heater box would need to be changed, or just need the evaporator put in the one in your truck. It’s probably the same heater box in your truck without the evaporator in it but I can’t say for sure. If you look at your heater box you may find a couple of blank flat spots on it that look suspiciously like where hoses might go into it through. If you find those your heater box just needs the evaporator installed and the punch-outs made for the hoses. Obviously the hoses from a donor are probably templates for you to have a hose shop make up new ones from at this point, but the hoses they make up for you will be the right length with the right fittings.. You actually gain on this one because the old girl is a cab over, if it has a rad mounted condenser then all the hoses are short. In those installations the condenser, evaporator and compressor are all right handy to one another. You could probably touch all the major components of the a/c system standing in one spot. Finding a shop manual for that truck would be a huge benefit to you, in general, not just for the a/c project.

 

There's a truck literally identical to yours on truck paper for 5 grand in Fremont. If it had an AC system it might be worth it just to buy that whole truck and use whatever you need off it lol

https://www.truckpaper.com/listings/trucks/for-sale/213219845/1988-white-gmc-wh64t

 

You won’t need 50 unless you install two AC units. Most older campgrounds are only wired for 30A and you can run it no problem. What about wiring it for external power as well and running a generator?

 

Rooftop air conditioners draw a significant amount of electrical power. While some RVs may have a generator or an inverter system to support this, however, it's not recommended to use the air conditioner while driving because it can strain the vehicle's electrical system and potentially drain the battery faster.

 

A motorhome that can run RV AC while driving is essential.

 

Harbor freight PREDATOR Inverter style will be plenty and very very quiet compared to regular noisy gensets.

Adding AC to the truck engine isn't that difficult, you can buy aftermarket AC kits and components.
You'll need to install the condenser, AC compressor, lines, wiring and evaporator box in the truck. Yeah you'll have to fab some things but having the daytime solution and a nighttime solution will be extremely nice for a full timer.


Oh .. if you want to run bigger AC loads a factory 160 amp alternator isn't going to cut it... You'll want a 300amp brushless or bigger. I have the delco 300a brushless and it's a beast running my Xantrex Inverter