LEMON Manuals: Even more car manuals for everyone
Home >> Ford >> 1998 >> Mustang Base, 2D Convertible, Automatic >> Repair and Diagnosis >> Accessories & Equipment >> Gauges & Instrument Panels >> Instrument Panels - Analog >> Testing >> Oil Pressure Gauge Inaccurate

Oil Pressure Gauge Inaccurate

  1. Disconnect negative battery cable. Remove instrument cluster. See INSTRUMENT CLUSTER under REMOVAL & INSTALLATION. Disconnect cluster connectors C250 and C251. See Figure and Figure . Reconnect negative battery cable. Turn ignition on. Check voltage between ground and instrument cluster connector C251 terminal No. 4 (Red/Yellow wire). If battery voltage is present, go to next step. If battery voltage is not present, repair open in Red/Yellow wire and retest system.
  2. Using an ohmmeter, measure resistance between ground and cluster connector C251 terminal No. 2 (Black/Light Blue wire). If resistance is less than one ohm, go to next step. If resistance is more than one ohm, repair open in Black/Light Blue wire as required and retest system.
  3. Turn ignition off. Disconnect harness connector at oil pressure switch. Turn ignition switch on, wait 60 seconds and read gauge. If gauge reads "L" or below, go to next step. If gauge reads above "L", go to step 5).
    NOTE: If gauge reading is higher when heavy electrical loads are imposed, such as when cooling fan turns on, it is usually an indication that a poor ground path exists between switch and gauge.
  4. Connect oil pressure switch harness connector (White/Red wire) to ground. If gauge indicates mid-scale or slightly above, replace oil pressure switch and retest system. If gauge does not indicate mid-scale or above, go to next step.
    NOTE: There is a 10-ohm resistor on instrument cluster printed circuit between switch input and gauge. All other circuits should have less than 0.1 ohm resistance from printed circuit to gauge.
  5. Turn ignition off. Remove instrument cluster. See INSTRUMENT CLUSTER under REMOVAL & INSTALLATION. Using an ohmmeter, check resistance between cluster printed circuit connections and gauge. If resistance is less than 0.2 ohm through each cluster printed circuit, go to next step. If resistance is more than 0.2 ohm, replace instrument cluster printed circuit and retest system. See PRINTED CIRCUIT under REMOVAL & INSTALLATION.
  6. Check switch input wire, circuit No. 31 (White/Red wire) for continuity from switch connector to cluster connector C251 terminal No. 3. If resistance is less than 0.2 ohm, go to next step. If resistance is more than 0.2 ohm, check for corrosion and poor harness connections or repair open in White/Red wire. Repair as necessary and retest system.
  7. Check resistance between ground and oil pressure switch case. If resistance is less than 0.2 ohm, replace instrument cluster and retest system. See INSTRUMENT CLUSTER under REMOVAL & INSTALLATION. If resistance is more than 0.2 ohm, replace oil pressure switch and retest system.
scientia non olet · About LEMON Manuals