After going thru an extensive ac upgrade on my 73tii, there are some things everyone should be aware of:
1) New, parallel flow condensers will block more air used to cool an engine radiator. My engine temps were higher after installing a 10x18 condenser, even on a relatively cool day. My engine already had a 71 degree C thermostat, new water pump PLUS a new Walloth Nesch HF 3 row radiator.
2). Using the condenser fan (like a 12” Spal) for cooling the radiator (in my case) did not work effectively enough after I removed the stock 5 blade mechanical fan. I added it back to the engine which provided enough air to keep engine temps in line.
3) Use reduced barrier (RB) ac hoses for easier routing, especially in the cabin and nose areas. When using a crimping tool, you must crimp the RB fittings MORE than the instructions say, or else you may have leaks. BTDT. Standard thickness hoses are more forgiving for leaks due to the extra material.
4). Bypass the original relay in the Behr system that prevents the ac from turning on if the heater blower is on. Too much confusion for what should be a simple circuit.
5) Wire in a manual toggle switch for the condenser fan to activate it as required (supplements the stock mechanical fan for hot days).
6) Add a relay with in line fuse for the ac compressor instead of relying on the old switches which may have a large voltage drop. I mounted a relay next to the Spal condenser fan relay on the right inner fender.
7) Move the AC charge point fittings away from the compressor and exhaust manifold. There are quite a few options for fittings.
8). Source some copper flare washers for use at the original evaporator and expansion valve. Contrary to the published Behr documentation, the small fitting on the evaporator valve is different than listed. Gasket 5 says 7/16” washer. It is actually 1/4”.
9) A new ac temperature switch is cheap. I sourced a new one via Amazon for less than $9. UAC brand p/n SW6490C. It doesn’t come with a knob, but you can press your old one on.