Help me understand fuel quantity gauge internal wiring

Thread Starter

jethro99

Joined Oct 31, 2020
17
With respect to a common automotive type of fuel quantity gauge, most of the diagrams I find on the inner web show battery power being provided to one side of two coils within the gauge. With the lead from the sender being connected to the junction of the two coils. Like this below:


But a diagram I found in an FAA manual shows power being applied to the junction of the two coils. With the lead from the sender being connected to one side of one of the two coils. Like this below:


Are these just two ways of achieving the same means to an end?

Or is it the situation that with respect to the first diagram if the sender is disconnected the gauge will read full whereas with respect to the second diagram if the sender is disconnected the gauge will read empty?
 

KeithWalker

Joined Jul 10, 2017
2,312
In both cases that you show, there is a fixed current through the left coil and the current through the right coil varies with the amount of resistance in series with it. They will both work the same way with the needle being deflected by the difference between the opposing magnetic fields generated by the two coils.
 
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