How to Troubleshoot an Automotive Fuel Gauge

Video Transcript

"Talking about fuel gauge issues and how do you how do you diagnose, or what what the concern is with the fuel gauge. This is an older type electrical fuel gauge that you'll find in many, many of the older vehicles. The newer ones use electronically actuated gauges, but this is the dash unit right here, and obviously the gauge doesn't read correctly. Sometimes it can read all the way full and never go down, and sometimes it could read empty all the time and once in a while someplace in between. And what you want to determine first of all is whether or not, you know, you have gas in the tank, so you want to know get an idea of how much fuel is in the tank. And in the tank is a sending unit that actually is a little float assembly, and a and a rheostat type of arrangement there, and the float actually floats up and down on the gasoline; has a little pointer that rubs on a coil, and it has varying resistance. And that varying amount of current goes up to this dash unit right here and it interprets that signal and tells you the level of fuel that's that's in the, that's in the tank. And usually it's the tank sending unit that's going bad because that's mechanical. Either the float develops a hole and starts to sink, or that little contact that rubs on the on that rheostat coil wears out and sticks or the coil breaks and it sticks in one spot and you don't get a good reading, so that that can cause that that particular issue. Another thing that we have on these gauges is what's called a constant voltage regulator. If you have an oil pressure gauge or a fuel gauge, and a temperature gauge and the gauge reads high all the time or reads low all the time it could be your instrument voltage regulator or constant voltage regulator which fits in behind there. And what it actually does is takes the car system voltage and drops it down to about five volts instead of twelve volts so that if you get a fluctuation in voltage it's not going to cause the gauges to go up and down, up and down and read all over the place. Newer cars use electronic fuel gauges so you you have to use your scan tool and actually scan the computer and look for concerns with with the fuel gauge. And a lot of times there are updates or programs where you can actually reflash the computer to fix the fuel gauge, so you can actually fix the fuel gauge electronically by reflashing the program. You usually have to go back to the dealership because they have the software for that type of operation, and all they do is plug it into a car's computer system and they can actually set it to reprogram itself."