Thanks, I am working a fan upgrade now.
I've got a bulb holder and wire into the back of the Speedo in the proper location.
Mine is an "L" Model (#5357).
I'm not going to argue with the experts, I would have guessed that the light would have been triggered by the LOWER temperature sender, but....
Thanks for the clues. I'll be work it!
Rocky
(a.k.a. Chuck)