A: Fuel Level Reads Erroneously

A1 VERIFY POWER AT FUSE PANEL - LOAD SIDE


^ Key ON.


^ Using Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent verify system voltage at the load side of fuse.


^ Is the voltage greater than 10 volts?


Yes

GO to A3.


No

GO to A2.



A2 VERIFY POWER AT FUSE PANEL - FEED SIDE


^ Key ON.


^ Using Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent verify system voltage at the feed side of the fuse.


^ Is the voltage greater than 10 volts?


Yes

REPLACE the fuse.


No

REPAIR the wiring to the fuse panel.



A3 VERIFY POWER AT CLUSTER


^ Have cluster connector(s) remain intact.


^ Partially remove the instrument cluster from the instrument panel


^ Key ON.


^ Measure the voltage on the ignition wire at the instrument cluster connector to ground.


^ Is the voltage greater than 10 volts?


Yes

GO to A4.


No

REPAIR the ignition wire.



A4 VERIFY GROUND CIRCUITRY AT CLUSTER

CAUTION: Before checking the continuity of any circuit, make sure there is no voltage present in the circuit prior to switching the test equipment to the resistance


function to avoid damage to equipment. Refer to the test equipment user's manual for additional information.


^ Use an ohmmeter to check the continuity of the ground wire at the instrument cluster connector to ground.


^ Is the resistance less than 1 ohm?


Yes

GO to A5.


No

REPAIR the wire to ground.


A5 CHECK FUEL GAUGE (EMPTY)


^ Key OFF.


^ Disconnect the fuel gauge sending unit.


^ Connect one lead of the Rotunda Instrument Gauge System Tester (021-00055) or equivalent to the fuel sending unit input wire at the fuel gauge sending unit connector and the other lead to ground.


^ Set the tester to 22 ohms.


^ Key ON.


^ Wait one minute.


^ Read the fuel gauge.


^ Does the fuel gauge read E (empty)?


Yes

GO to A9.


No

GO to A6.



A6 RE-CHECK FUEL GAUGE (EMPTY)


^ Place the key in the OFF position. Then to the ON position. Tap on the instrument panel


^ Wait one minute.


^ Read the fuel gauge.


^ Does the fuel gauge read E (empty)?


Yes

GO to A9.


No

GO to A7.



A7 CHECK PRINTED CIRCUIT BOARD


^ Key OFF.


^ Disconnect the instrument cluster and instrument cluster gauge amplifier.


^ Measure the resistance of the circuit between the "SIG" terminal of the fuel gauge and the instrument cluster gauge amplifier.


^ Is the resistance less than 1 ohm?


Yes

GO to A8.


No

Ranger/Explorer: REPLACE instrument cluster printed circuit. Aerostar: REPLACE Instrument Cluster.



A8 CHECK INSTRUMENT CLUSTER GAUGE AMPLIFIER (EMPTY)


^ Turn the key to OFF position. Remove the instrument cluster. Inspect the instrument cluster printed circuit.


^ Remove the instrument cluster gauge amplifier. Connect a jumper wire from the Rotunda Instrument Gauge System Tester 021-00055 or equivalent directly to the fuel gauge "SIG" terminal.


^ Install the instrument cluster.


^ Turn the key to the ON position.


^ Read the fuel gauge.


Does the fuel gauge read E (empty)?







Yes

REPLACE the instrument cluster gauge amplifier. GO to A5


No

REPLACE the fuel gauge. INSTALL the instrument cluster gauge amplifier and RETURN to A5



A9 CHECK FUEL GAUGE SENDING UNIT WIRE


^ Key OFF.


^ Disconnect the instrument cluster and the fuel gauge sending unit.


^ Measure the resistance of the "Y/W" wire between the instrument cluster and the fuel gauge sending unit.


^ Is the resistance less than 1 ohm?


Yes

GO to A10


No

SERVICE the Y/W wire between the instrument cluster and the fuel gauge sending unit.



A1O CHECK FUEL SENDING UNIT GROUND


^ Key OFF.


^ Measure the resistance of the "O" (Ranger and Explorer) or "BK/W" (Aerostar) wire at the fuel gauge sending unit connector to ground at battery.


^ Is the resistance less than 1 ohm?


Yes

GO to A11


No

SERVICE the "O" (Ranger and Explorer) or "BK/W" (Aerostar) wire from the fuel gauge sending unit to ground.



A11 CHECK FUEL GAUGE (FULL)


^ Key OFF.


^ Disconnect the fuel gauge sending unit.


^ Connect one lead of the Rotunda Instrument Gauge System Tester 021-00055 or equivalent to the "Y/W" wire at the fuel gauge sending unit connector and the other lead to ground.


^ Set the tester to 145 ohms.


^ Key ON.


^ Wait one minute.


^ Read the fuel gauge.


^ Does the fuel gauge read F (full)?

Yes

GO to A13.


No

GO to A12.



A12 CHECK INSTRUMENT CLUSTER GAUGE AMPLIFIER (FULL)

^ Turn the key to OFF position. Remove the instrument cluster. Inspect the instrument cluster printed circuit. Remove the instrument cluster gauge amplifier. Connect the jumper wire from the Rotunda Instrument Gauge System Tester 021-00055 or equivalent directly to the fuel gauge "SIG" terminal.


^ Install the instrument cluster.


^ Turn the key to the ON position.


^ Read the fuel gauge.


^ Does the fuel gauge read F (full)?


Yes

REPLACE the instrument cluster gauge amplifier. GO to A5


No

REPLACE the fuel gauge. RETURN to A5



A13 FUEL TANK INSPECTION


^ Inspect fuel tank for distortion or damage.


^ Is fuel tank damaged?


Yes

REPLACE fuel tank.


No

GO to A14.



A14 TEST BOX CHECK - EMPTY STOP


^ Connect one lead of a Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent to the fuel sender signal lead and the other lead to sender ground.


^ When the float rod is against the empty stop (closest to fuel filter).


^ Does DVOM read 14-18 ohms?


Yes

GO to A15.


No

REPLACE fuel sender.



A15 TEST BOX CHECK - FULL STOP


^ Connect one lead of a Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent to the fuel sender signal lead and the other lead to sender ground.


^ When the float rod is against the full stop.


^ Does DVOM read 154-162 ohms?


Yes

GO to A16.


No, less than 154 or greater than 162 ohms

REPLACE fuel sender.



A16 TEST BOX CHECK - FLOAT ROD TRAVEL


^ Connect one lead of a Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent to the fuel sender signal lead and the other lead to sender ground.



^ Move float rod slowly from FULL to EMPTY stop position.


^ Does ohmmeter reading decrease slowly?


Yes

GO to A17.


No

REPLACE fuel sender.



A17 HARNESS CONNECTOR CHECK - EMPTY STOP


^ Re-attach all fuel indication connectors.


^ Move float rod to empty stop position.


^ Place key in the ON position.


^ Wait 60 seconds.


^ Read fuel gauge.


^ Does fuel gauge read empty?


Yes

GO to A18.


No

GO to A7.



A18 HARNESS CONNECTOR CHECK - FULL STOP


^ Re-attach all fuel indication connectors.


^ Move float rod to full stop position.


^ Place key in the ON position.


^ Wait 60 seconds.


^ Read fuel gauge.


^ Does fuel gauge read full?


Yes

GO to A19.


No

GO to A7.



A19 INSPECT FUEL SENDER


^ Inspect float and float rod.


^ Is float rod distorted, hitting filter, filled with fuel or loose on float rod?


Yes

REPLACE sender.


No

GO to A20.



A20 PIGTAIL HARNESS CHECK - EXPLORER

^ Connect one lead of a Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent to the fuel sender signal lead in the pigtail connector and the other lead to the corresponding below the flange rivet.


^ Check sending unit ground circuit in same manner as above.


Is ohmmeter reading greater than 1 ohm?


Yes

REPLACE fuel sending unit.


No

Pigtail OK.