 Electrical Question, Fuel Gauge reading jumps with lights on... |
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| jim_hoyland |
 Sep 1 2014, 09:03 AM
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#1
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Get that VIN ?  Group: Members Posts: 9,319 Joined: 1-May 03 From: Sunset Beach, CA Member No.: 643 Region Association: Southern California 
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This has been bugging me for several years; every time the light switch is "ON", the fuel gauge level jumps up almost 1/4 tank.
I have a Getty 5 gauge dash: Clock, Speedo, Tach, Oil Press/Temp, and Fuel/Voltmeter. All the gauges share a common ground and common voltage source for the gauge lights; I'm wondering whether one or both need to be isolated to prevent the interference? Need some electriccal input here... (IMG:style_emoticons/default/smile.gif) |
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| stugray |
Sep 1 2014, 01:01 PM
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#2
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Advanced Member Group: Members Posts: 3,825 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
You have a bad ground.
When the lights are on, more current flows through the ground path from the light switch to the battery. A high resistance in the ground path means that the extra current causes a bigger voltage drop in the return path. This means that the gauge sees a smaller voltage from the sensor because the voltage drop in the ground path is shifting the reference voltage up. |
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Posts in this topic
jim_hoyland Electrical Question Sep 1 2014, 09:03 AM
904svo When I put a Subby in my kit car I ran inti the sa... Sep 1 2014, 12:36 PM Tom 904svo,
you hit the nail on the head! Wit... Sep 1 2014, 12:55 PM Tom 904svo,
you hit the nail on the head! Wit... Sep 1 2014, 12:55 PM jim_hoyland Thanks for the inputs: should the Fuel/Voltmeter g... Sep 1 2014, 03:05 PM
Marty Yeoman My car exhibits the same phenomena. I'm just a... Sep 2 2014, 01:28 PM |
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