Fuel sending unit wiring

[hunter1]

This may be a dumb question but does the voltage "pulse" going to the fuel tank sending unit? I wouldn't think so but I'm tracing wiring to the rear and the sending unit wiring was making my test light blink dimly. I got my fluke and checked it and the same thing, voltage jumping around. I don't have an analog meter to check it with tonight. Can get one tomorrow, but thought for sure someone here knows?

 

[hunter1]

This may be a dumb question but does the voltage "pulse" going to the fuel tank sending unit? I wouldn't think so but I'm tracing wiring to the rear and the sending unit wiring was making my test light blink dimly. I got my fluke and checked it and the same thing, voltage jumping around. I don't have an analog meter to check it with tonight. Can get one tomorrow, but thought for sure someone here knows?

Is it because it's going through the gauge first?

 

[hunter1]

Is it because it's going through the gauge first?

Probably because I'm grounding it through the light or meter and not the resister strip on the sending unit?

 

[Oldtimer]

The instrument voltage regulator (IVR) on the back of the instrument cluster drops 12v down to approx 5v, and it is a pulsing voltage. The lower voltage is supplied to oil, temp, & fuel gages, and then continues to ground thru their respective sensors.
What you are seeing is "normal".

1976 Ford Bronco Tech Diagrams picture | SuperMotors.net

wiring72strip.jpg 1972 Bronco Wiring Diagram IF THE IMAGE IS TOO SMALL, click it. Improved, corrected, & combined version of [url=http://seabiscuit68.tripod.com/]Seabiscuit[/url]'s colorized diagrams. This is an early version - I may delete & re-upload it several more times with corrections...

www.supermotors.net

 

[DirtDonk]

Because the pulsing is consistent, and the gauge’s action is dampened, the reading on the gauge is able to be read consistently, and even compensate for different ambient temperatures.
The standard electro-mechanical point type IVR’s are still available, but there are also electronic versions which give a steady output voltage that can be read by a modern digital volt meter.
So no figuring out what the average is, or getting an analog gauge because most digital instruments are hard read properly with the pulse.

 

[hunter1]

Thanks guys. Makes me feel better knowing that it’s not a problem.