Seems like a question about the fuel gauge comes up about once a week.
I believe even a fifth grade student could understand the workings from this
drawing that is circulating on the internet:
http://www.pbase.com/dennygraham/image/159356931 You’re working with a basic series/parallel circuit in which the current runs thru
the first winding (load) then splits into two legs for the current to flow to ground.
One is thru the second winding in the dash gauge to ground.
The other path is to the Sender winding to ground.
When the wiper at the sender is in the empty position it offers no opposition to the
current flow and since current follows the path of least resistance all of it will seek
ground through this path and none will pass through the gauge.
When the wiper at the sender is in the full position it offers a very high resistance to
current flow in relation to the meter and the vast majority of the current flows through
the gauge sensing coil and the needle show full.
If the circuit is open between the gauge to the sender or if the sender is stuck in the
full position then the gauge will read full.
If the circuit is shorted between the gauge and the sender then no or very little current
will flow through the Gauge sensing winding and it will read empty.
That’s basically all there is to it.
Denny Graham
All gassed up in Sandwich, IL
