Is there some sort of hidden switch in a 1985 300CD sunroof circuit that prevents power going to the motor based on position? My sunroof will open, but receives no power to close. I initially thought it was the switch, but trying a new switch and then hot wiring the motor at the switch produce no power to the motor.

Just for posterity, the answer is there is no hidden switch. The sunroof motor is only powered by the switch on the dash. It turns out that my spare switch was just another bad switch. I took the switch apart and rebuilt it by cleaning the contacts with emery paper and Caig's Deoxit and replacing the crusty grease with new Krytox 205 grease. Should be good for another 20 years. For a 1985 300 CD switch there are four wires on the switch:

Black is from power from the fuse - Center pin, only pin on one side, fat wire
Green goes to motor
Brown goes to ground
Blue goes to motor
Thin black "wire" is the fiber optic lead

Thanks for the follow-up! Yeah, I woulda said it's just a simple circuit, but you really can never truly rule out substituted parts.

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'82 300CD
"Pearl", the very first turbo diesel 123 coupe
Totaled 11/23/18, rebuild in progress.
'85 300TD, "Artemis".
'78 300D euro, "Ol' Red", mostly retired.
'85 300D, "Gandalf".