[WalterBright]

I read about this probably 10 years ago, my memory was clearly a bit faulty on it. I didn't want to take the device on my Dodge apart just to verify it :-).

The thing is, the instruments require the noisy 5V.

You can buy kits with an electronic 5V source, and also to replace the old guts of the instruments with modern ones. That retains the original look, with modern accuracy and performance.