Hi, I recently swapped in a tach/clock combination on my 300D.

But, my clock doesnt work.

Are these all the same if needed to repair or are they different?

The clock is powered by a single spade terminal on the back connected to a constant-hot source. It is grounded through the metal on the mounting bracket. That's really all there is to powering up the clock. Be aware that there are a couple of electrolytic capacitors (you can see them in your photo) that are prone to failure, and when they go they will prevent the clock from operating. If your wiring is good, replace those caps (replace them anyway for good measure!) and your clock should run.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

I know I will try with another source.

Thank you for your answer.

how to remove backplate?