C: Oil Pressure Reads Erroneously

C1 VERIFY POWER AT FUSE PANEL - LOAD SIDE


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


^ Is system voltage present at load side of fuse?


Yes

GO to C3


No

GO to C2.



C2 VERIFY POWER AT FUSE PANEL - LOAD SIDE


^ Using Rotunda Digital Volt-Ohmmeterol4-00407 or equivalent verify system voltage at feed side of warning indicator fuse.


^ Is system voltage present at feed side of fuse?


Yes

REPLACE fuse.


No

SERVICE wiring to fuse panel.



C3 VERIFY POWER AT CLUSTER - FEED SIDE


^ Partially remove cluster from IP. Using Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent verify system voltage at cluster connector and/or gauge terminal.


^ Inspect cluster connector for damage.


Is voltage present at cluster connector and gauge terminal?


Yes

GO to C4.


No

SERVICE as required.



C4 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.


^ Using Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent check continuity of instrument cluster and gauge ground circuitry.


^ Is ground circuitry good?


Yes

GO to C5


No

SERVICE as required.



C5 TEST SENDER CIRCUIT AT LOW


^ Place key in the ON position with engine off. Observe gauge performance.


^ Does the gauge read L or below?


Yes

GO to G6.


No

GO to C7



C6 CHECK GAUGE RESPONSE


^ Disconnect oil pressure switch and short the lead to engine ground.


^ Does the gauge indicate approximately mid-scale or slightly above mid-scale (around the MAL in NORMAL)?


Yes

REPLACE oil pressure switch.

No

GO to C7.



C7 CHECK SENDING UNIT/SWITCH WIRING



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.


^ Using Rotunda Digital Volt-Ohmmeter 014-00407 or equivalent check sending unit/switch wiring and instrument cluster printed circuit for shorts or opens by physically flexing the wiring and observing continuity. The continuity reading should not fluctuate.


^ Gauge will read beyond the normal band if not grounded.


^ Is wiring and instrument cluster printed circuit OK?


Yes

REPLACE gauge.


No

Aerostar: SERVICE wiring or REPLACE the instrument cluster. Ranger/Explorer: SERVICE wiring or REPLACE instrument cluster printed circuit.