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Fuel Gauge & Sending Unit Test

  1. Using a DVOM with ignition switch in ON position, verify battery voltage at load side of fuse No. 18. See Figure . If voltage is 10 volts or more at load side of fuse, go to step 3). If voltage is less than 10 volts, go to next step.
  2. Using voltmeter, verify voltage at feed side of fuse No. 18. If voltage is 10 volts or more, replace fuse and retest system. If voltage is less than 10 volts, repair wiring to fuse panel and retest system.
  3. Partially remove cluster from instrument panel. See INSTRUMENT CLUSTER R & I  under REMOVAL & INSTALLATION. Turn ignition switch to ON position. Using voltmeter, verify battery voltage from cluster connector C2, terminal No. 12 (Red/Yellow wire) to ground. See Figure . If battery voltage is present, go to next step. If voltage is not present, repair circuit No. 640 (Red/Yellow wire) and retest system.
  4. Turn ignition switch to OFF position. Using an ohmmeter, check continuity of ground wire from instrument cluster connector C2, terminal No. 13 to ground. If resistance is less than one ohm, go to next step. If resistance is more than one ohm, repair circuit No. 570 (Black/White wire) and retest system.
  5. With ignition switch in OFF position, disconnect fuel gauge sending unit. Using Instrument System Gauge System Tester (021-00055), connect one tester lead to fuel sending unit input wire, circuit No. 29 (Yellow/Red wire) at fuel gauge sending unit connector. Connect second lead to ground. Set tester to 22 ohms. Turn ignition switch to ON position. Wait one minute and read fuel gauge. If fuel gauge reads "E", go to step 9). If gauge does not read "E", go to next step.
  6. Turn ignition switch to OFF position and then to ON position. Tap on instrument panel. Wait one minute and read fuel gauge. If fuel gauge reads "E", go to step 9). If gauge does not read "E", go to next step.
  7. With ignition switch in OFF position, disconnect instrument cluster and instrument cluster gauge amplifier. See Fig 1 . Measure resistance of circuit between SIG terminal of fuel gauge and instrument cluster gauge amplifier. If resistance is less than one ohm, go to next step. If resistance is more than one ohm, replace instrument cluster. See INSTRUMENT CLUSTER R & I  under REMOVAL & INSTALLATION.
    Fig 1: Locating Instrument Gauge Cluster Amplifier (Aerostar)
    G95J35401Courtesy of FORD MOTOR CO.
  8. Turn ignition switch to OFF position. Remove instrument cluster. See INSTRUMENT CLUSTER R & I  under REMOVAL & INSTALLATION. Inspect instrument cluster printed circuit. Remove instrument cluster gauge amplifier. Connect a jumper wire from Instrument Gauge System Tester (021-00055) directly to fuel gauge SIG terminal. Install instrument cluster. See Fig 1 . Turn ignition switch to ON position. Read fuel gauge. If fuel gauge reads "E", replace instrument cluster gauge amplifier. See INSTRUMENT CLUSTER GAUGE AMPLIFIER  under REMOVAL & INSTALLATION. Go to step 5). If fuel gauge does not read "E", replace fuel gauge. See FUEL GAUGE  under REMOVAL & INSTALLATION. Install instrument cluster gauge amplifier. See the INSTRUMENT CLUSTER GAUGE AMPLIFIER  under REMOVAL & INSTALLATION. Go to step 5).
  9. Turn ignition switch to OFF position. Disconnect instrument cluster and fuel gauge sending unit. Measure resistance of circuit No. 29 (Yellow/White wire) between instrument cluster and fuel gauge sending unit. If resistance is less than one ohm, go to next step. If resistance is more than one ohm, repair circuit No. 29 (Yellow/White wire). If resistance is less than one ohm, go to step 10). If resistance is more than one ohm, repair circuit No. 29 (Yellow/White wire). Retest system. See Figure .
  10. With ignition switch in OFF position, measure resistance of circuit No. 397 (Black/White wire) at fuel gauge sending unit connector to battery ground. If resistance is less than one ohm, go to next step. If resistance is more than one ohm, repair circuit No. 397 (Black/White wire) from fuel gauge sending unit to ground.
  11. With ignition switch in OFF position, disconnect fuel gauge sending unit. Using Instrument System Gauge System Tester (021-00055), connect one tester lead to fuel sending unit input wire, circuit No. 29 (Yellow/Red wire) at fuel gauge sending unit connector. Connect second lead to ground. Set tester to 145 ohms. Turn ignition switch to ON position. Wait one minute and read fuel gauge. If fuel gauge reads "F", go to step 13). If gauge does not read "F", go to next step.
  12. Turn ignition switch to OFF position. Remove instrument cluster. See INSTRUMENT CLUSTER R & I  under REMOVAL & INSTALLATION. Inspect instrument cluster printed circuit. Remove instrument cluster gauge amplifier. See Fig 1 . Connect a jumper wire from Instrument Gauge System Tester (021-00055) directly to fuel gauge SIG terminal. Install instrument cluster. Turn ignition switch to ON position. Read fuel gauge. If fuel gauge reads "F", replace instrument cluster gauge amplifier. See INSTRUMENT CLUSTER GAUGE AMPLIFIER  under REMOVAL & INSTALLATION. Go to step 5). If fuel gauge does not read "F", replace fuel gauge. See FUEL GAUGE  under REMOVAL & INSTALLATION. Install instrument cluster gauge amplifier. See, under REMOVAL & INSTALLATION, INSTRUMENT CLUSTER GAUGE AMPLIFIER  . Go to step 5).
  13. Inspect fuel tank for distortion or damage. If fuel tank is damaged, replace fuel tank. If fuel tank is undamaged, go to next step.
  14. With an ohmmeter, connect one lead to fuel tank sender signal lead circuit No. 29 (Yellow/White wire) and other lead to sender ground circuit No. 397 (Black/White wire). If ohmmeter reads 14-18 ohms when float rod is closest to fuel filter (empty stop), go to next step. If resistance is not 14-18 ohms, replace fuel sender.
  15. Using an ohmmeter, connect one lead to fuel sender signal lead circuit No. 29 (Yellow/White wire) and the other lead to sender ground circuit No. 397 (Black/White wire). If resistance is 154-162 ohms with float rod against full stop, go to next step. If resistance is less than 154 or more than 162 ohms, replace fuel sender.
  16. Using an ohmmeter, connect one lead to fuel sender signal lead circuit No. 29 (Yellow/White wire) and the other lead to sender ground circuit No. 397 (Black/White wire). Move float rod slowly from full to empty stop position. If ohmmeter reading slowly decreases, go to next step. If resistance does not change or changes radically (jumps), replace fuel sender.
  17. Reattach all fuel indication connectors. Move float rod to empty-stop position. Turn ignition switch to ON position. Wait 60 seconds and read fuel gauge. If fuel gauge reads empty, go to next step. If gauge does not read empty, go to step 7).
  18. Turn ignition switch to OFF position. Move float rod to full-stop position. Turn ignition switch to ON position. Wait 60 seconds and read fuel gauge. If fuel gauge reads full, go to next step. If gauge does not read full, go to step 7).
  19. Inspect float and float rod. If float or float rod is distorted, hitting filter, filled with fuel or loose on float rod, replace fuel sender. If condition is okay, go to next step.
  20. Using an ohmmeter, connect one lead to fuel sender signal lead circuit No. 29 (Yellow/White wire) in pigtail connector and the other lead to corresponding wire below flange rivet. Check ground circuit No. 397 (Black/White wire) in the same manner. If resistance is greater than one ohm, replace sending unit. If resistance is one ohm or less, pigtail is okay.
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