GMC 1976 ZEO 6083 Maintenance Manual page 618

2. Ground connection-one-way connector from
tank to ground.
3. Body harness connector-l0-way connector at
instrument panel .
4. Body harness connector to printed circuit at
gauge.
5 . Mounting screws holding gauge to panel .
6. Make sure gauge pointer is not contacting face
of gauge or lens .
7. Fuel selector switch connections.
GAUGE ALWAYS REGISTERS FULL
(WITH IGNITION SWITCH ON)
Most probable cause is an open circuit in wiring
or tank unit .
1. Check ground wires from tank units to ground .
If loose, clean terminals, reinstall and check gauge
reading.
2. Connect a spare tank unit to tank wiring . Raise
and lower the float arm slowly, observing the dash
unit (Be sure selector switch is in the appropriate
position).
a. If dash unit does not function an open cir-
cuit at dash or tank unit is indicated.
b. If dash unit follows the arm movement
proceed to step 3.
3. Inspect the wire terminals at the tank unit after
lowering the fuel tank . If connection is loose, clean
terminals and reinstall wires. If gauge continues to
register "FULL" (with tank empty), remove the
tank unit . Reconnect the wiring with unit out of
tank, including the ground and move float arm. If
dash unit does not follow arm movement, replace the
tank _unit.
GAUGE ALWAYS REGISTER EMPTY
(WITH IGNITION SWITCH ON)
Most probable cause is a grounded circuit in the
wiring due to a pinched or cut wire, or shorted fuel
gauge dash unit . Disconnect the tank unit feed wire
at the tank . The dash unit gauge should now register
FULL .
Gauge Continues To Read Empty
1 . Remove the instrument panel rear cover.
CHASSIS ELECTRICAL 1 2- 13
2. Remove the fuel gauge wire from the 7-wire
connector on the gauge head (GRAY/DBL BLACK
STR) .
3. Gauge should now read FULL . If the gauge
continues to read EMPTY, replace the dash unit .
Gauge Now Registers Full
1 . Connect a spare tank unit to the tank feed wire
at the body harness connector and ground unit at
flange to chassis with a jumper wire .
2. Raise and lower float arm assembly while ob-
serving the dash unit .
a. If dash unit still does not operate, replace
the dash unit after a continuity check of printed
circuit has been made .
b. If the dash gauge follows the float arm
movement, check tank unit feed wire for insulation
breakdown. If wire is okay, replace the tank unit .
3 . Check tank unit for improper installation of
fuel filter screen which could restrict float move-
ment .
4. If dash unit still does not follow the tank unit
arm movement, replace the tank unit .
WATER TEMPERATURE GAUGE
When checking the water temperature gauge cir-
cuit, determine whether engine temperature sending
unit, wiring, dash unit or printed circuit is faulty .
To check the engine water temperature sending
unit, proceed as follows:
1. Disconnect wire at engine unit .
2. Connect a test light consisting of a 12V-2 can-
dle power bulb and a pair of test leads in circuit by
clipping one lead to battery positive terminal and
other lead to body of engine gauge unit . If bulb lights,
unit is properly grounded . If bulb does not light,
check for presence of sealing compound around
threads of unit . Remove compound and repeat test .
3. Remove test lead from body of unit and con-
nect lead to terminal of unit . If bulb lights, engine
unit is internally shorted and should be replaced .
nal.
4. Remove test light and reinstall wire on termi-
5. If engine unit tests satisfactory under previous
conditions, check the following items according to
nature of difficulty :