Originally Posted by Diseasel300

Not as much as it will a Gen 1 W126 or a W123. The small-tube dual-circuit condenser of the Gen II W126 is quite efficient. It also has the huge benefit that it can be flushed, a parallel flow condenser cannot and must be replaced if clogged or compressor fails.
Use PAO68 oil. It is usable with R12 or R134a. All of it goes in the compressor, the Densos have a sump and do not require the oil distributed around the system.


Replacement monovalve core should ONLY come from the dealer. They're expensive ($130 or so) but the only ones that work and last. An old hardened core will not work, the MTC aftermarket ones typically don't work properly either. Make sure your coolant hoses are routed correctly.

You have not confirmed whether or not the coil is energized with the A/C running, you can only test it properly with everything hooked up due to how the transistor pack in the pushbutton unit does its switching. Adding a manual valve is totally unnecessary, the monovalve should stop all water flow to the heater core when the temperature wheel is set to the blue dot (max cold).