|
If
you understand how a gas gauge is supposed to work, then finding
your problem will be much easier. Here is how most (AC) type
electric gas  gauges
work. Two parts make up the fuel gauge system, the dash gauge,
and the gas tank sender, located at the gas tank. Power to
the dash gauge is received from the "switched" side of the
ignition switch which means the dash gauge works ONLY when
the ignition switch is in the ON position. There is a small
counter weight located on the needle of the gauge which returns
the gauge needle to the EMPTY position when the ignition key
is in the off position.
With
the ignition key in the ON position current flows from the
ignition switch thru the small operating coil (located on
the back of the dash gauge), on to a "CHOKE" coil. From there
the current travels to a common terminal between the two coils.
After the current reaches the common terminal between the
coils the current travels back thru the operating coils, and
then on to ground. At the same time current is also sent to
the tank sender where current travels thru the sender unit
and on to ground.
When
the tank is empty the float will be near the bottom of the
tank so most of the current is sent directly to the tank sender
where it passes on to ground. As more fuel is placed in the
tank the float is raised and more current is sent to the operating
coil of the dash gauge causing the needle to move closer to
the full mark. It is electrical friction (resistance) from
the gas tank sender that guides the current to either the
tank sender or the dash gauge.
|
1)
The most common cause of fuel gauge trouble is a poor ground
especially at the tank sender.
Make sure all wiring connections are tight, and free of
dirt and corrosion. A poor ground or loose connection to
a fuel gauge system is just like loose or dirty battery
cables to your starting system.
2) If your gauge needle remains on EMPTY when the ignition
key is turned on and gas tank is partially full, battery
current is NOT reaching the gauge. Connect a jumper wire
between ignition switch and dash gauge. If gauge works,
replace defective wiring between switch and gauge.
3) If dash gauge NEEDLE remains in ONE POSITION as ignition
switch is turned off and on, either the dash gauge or the
tank sender is defective. Ground the gas tank sender terminal
using a jumper wire, if dash gauge shows empty, gas tank
sender is defective. If the dash gauge needle does not move,
replace dash gauge.
4) If dash gauge reads EMPTY or LOWER than it should,
check for defective wiring between the dash gauge and the
tank sender unit. Also check for poor ground.
5) If dash gauge reads, EMPTY when the tank is actually
half full the wiring between the dash gauge and the tank
sender is defective or the dash gauge is defective. Disconnect
the wire at the gas tank sender terminal, if gauge still
reads empty, the dash gauge is defective.
6) If dash gauge reads, FULL when tank is known to be
only half full the wiring between the tank or the sender
is bad. Ground the gas tank sender terminal using a jumper
wire, if the dash gauge still shows full there is bad wiring
between the dash gauge and the tank sender. If the dash
gauge goes to empty, the gas tank sender is defective. |
