|
|
Posted by Sherman in Idaho [72.47.9.37] on Monday, October 22, 2012 at 10:48:56 :
In Reply to: Fuel Gauge Question posted by gmharris [71.105.35.169] on Monday, October 22, 2012 at 00:06:31 :
I have not attempted to fix those kind, but I've played with them a bit on some other vehicle. If it's the kind I'm thinking of, there is a bimetallic "spring" in the sender as well as in the gauge. Maybe not on the Dodge version. Anyway, the idea is that the amount of current going through the gauge heats the spring in such a way as to make the contact points open, at which point the current stops and they close again. The contacts are constantly vibrating slightly, rather like the points in a mechanical voltage regulator, except under the influence of heat rather than magnetism. The stronger the current, the quicker they open in each cycle. The variation in the percent of time that they're open (what we would call "pulse width modulation" today) determines how hard the contraption pushes on the mechanism that moves the pointer. The advantages of this system are 1) it's cheap and 2) it provides a slow response so that the needle doesn't jump around as the fuel sloshes in the tank. The disadvantage is it doesn't really have any sort of accuracy at all, but that's okay for a gas gauge.
Follow Ups: