GMC 1976 ZEO 6083 Maintenance Manual page 616

CHASSIS ELECTRICAL 12- 1 1
IGNITION SWITCH
BATTERY
4 . If 1, 2, and 3 above are OK, in-
spect tank unit ground and wire
to tank unit . Repair as necessary
to insure good electrical con-
nections and no shorts through-
out .
5 . If fuel gauge system is still not
functioning properly after com-
pleting Step 4, replace tank unit .
6 .
7 .
With vehicle on a level surface, disconnect. 2-way connector (located at left frame rail by fuel
tanks) . With fuel selector switch in "FUEL MAIN" position, insert GG3 Tester between wire
to dash unit (18 Tan) and ground . Then perform the following test :
Position ignition switch in "ON." DO NOT START ENGINE .
1 . With tester knob set at "Continuity," lamp should glow .
2 . With tester knob set at "0," dash unit should indicate "EMPTY ."
3 . With tester knob set at "90," dash unit should indicate "FULL ."
If any one of 1, 2, or 3 are not
OK, inspect wiring from ignition
switch to the rear wiring con-
nector (including grounds) . Re-
pair as necessary to insure good
electrical connections and no
shorts throughout .
If any one of 1, 2, or 3 are still
not OK after completing Step 6,
replace dash unit .
NOTE : After "FUEL MAIN" portion of circuit is checked, move selector switch to "FUEL
AUX" position and connect GG3 to other side of 2-way connector (18 tan double white stripe)
and repeat test .
A-4138
Figure 18-Fuel Gauge Switch Diagnosis (Method Using AC-663 Tester)