Instruments - Revised Oil Pressure Indicator Gauge Ckt
NUMBER: 92-U-74CORP.REF.NO: 318103
DATE: April 1993
SECTION: 8A, 8C
SUBJECT:
OIL PRESSURE INDICATOR GAUGE
MODEL/YEARS:
1992 SILHOUETTE
This bulletin is an update on a 1992-1/2 engineering change, to the 1992 Silhouette oil pressure indicator gauge.
The oil pressure gauge, for the 3.1L (VIN D) engine, was previously fed by a variable resistance oil pressure sender (Kelsey-Hayes). The variable resistance sender has been changed to an oil pressure switch (HI-Stat), with a 68 ohm resistor in parallel with it.
This engineering change will create a functional change in the operation of the oil pressure gauge. The oil pressure gauge will show a 3/4 scale reading during normal engine run conditions, on the 3.1L (VIN D) engine. It is normal for the oil pressure gauge to stay at a 3/4 scale reading, with the ignition switch in the "OFF" position.
The enclosed information reflect the changes in the schematics, diagnostic charts, and the circuit operation.
Reminder:
Always check the engine oil level first when performing diagnosis.
INSTRUMENT PANEL WIRING DIAGRAM
CHART # 6A
CHART # 6B
CIRCUIT OPERATION
OIL PRESSURE INDICATOR GAUGE (VIN D)
A two-position switch opens with oil pressure greater than approximately 24 kPa (3 psi), directing current flow in CKT 231 through a 68 ohm resistor to ground. This causes the Oil Pressure Indicator Gauge to deflect to approximately 3/4 scale.
OIL PRESSURE GAUGE (VIN L)
A variable resistor is part of the Oil Pressure Sender/Fuel Pump Switch. With no oil pressure, the resistance of the variable resistor is approximately 1.0 ohms. At an oil pressure of 550 kPa (80 psi) the resistance of the variable resistor is approximately 88 ohms. The Oil Pressure Gauge applies voltage through CKT 231 to the variable resistor in the Oil Pressure Sender/Fuel Pump Switch. As the resistance of the variable resistor increases, the Oil Pressure Gauge senses a larger voltage drop across the variable resistor, indicating high oil pressure. As the resistance of the variable resistor decreases, the Oil Pressure Gauge senses a smaller voltage drop across the variable resistor, indicating low oil pressure.