I have three clocks for my '72 Supreme. One that is installed in the car and two spares. In an effort to diagnose an electrical issue, on a whim, I measured the resistance of all three clocks. All three were disconnected with all lightning harnesses removed. To conduct the test, I put the positive lead of my meter on the terminal on the clock and the negative lead on the case.

As you can see in the results below, the one that is installed showed a much higher resistance than the two spares. Can anyone tell me why?

 

Maybe the ones with lower resistance have the contact points ( the ones that wind the clock) closed?