The relay is a black rectangular box with multy pins ....mounted vertically near the bottom of the assembly. You will have to pull back or remove the fender liner to get at it.

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1986 300E

I never did find the relay, I'm guessing the 124 and 123 are just different enough but I did finally get the sunroof working.
I was seeing +12v on both wires at the motor, one at a time depending on switch position so things looked OK there.
It did confound me a bit when hooking up +12 directly to the motor and having it not run, seems the motor feilds are not tied to the chassis ground so BOTH + and - need to be on the 2 wires in. Which is where defines the direction of the motor.
From what I found the switch in the dash is a funky sort of double pole arrangment that switches + and - on the 2 wires coming out of it from the 2 wires feeding it. I think the - was not switching correctly at the switch. Sprayed in a bunch of WD40 and worked the action several times, blew some air, ect.. Put it back in and things started going again!!!

Thanks!!!

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1985 300D
The rest:
1957 MGA (comatose)
1965 Falcon (sleeping)
1966 E-100 (rust test in progress)
1976 Ford 3400 D Tractor (workhorse)
1978 Mercury Zephyer (5L playtoy)
1995 Isuzu NPR D (fetcher)
1998 Subaru Legacy (Spare)
2000 Toyota Sienna (School bus)
2008 Toyota Prius (Commuter)