2.
Unscrew the unit from the manifold.
3.
catch spillage and cover the fitting on the manifold to prevent foreign matter from entering the system.
OIL PRESSURE SENDER TEST. (Refer to Chart 7901)
The oil pressure sender works on the relationship of pressure to resistance. As the pressure increases so does the resistance and inturn alters the position of the needle of the instrument.
To test the sender the following procedure should be followed:
1.
Connect a calibrated pressure source to the pressure port.
2.
Attach ohmmeter leads to the one pole extending from the sender and one to the sender itself.
3.
Raise and lower the pressure to the sender and crosscheck with the required tolerances in Chart 7901.
79-30-00 Page 79-5 Issued: April 1, 1997
CHART 7901. OIL PRESSURE SENDER TEST SPECIFICATIONS
Pressure (Psig) Resistance (Ohms) Tolerance(Ohms)
0 10 _
25 46 -5, +0
60 90 —
90 126 -0, +15
INSTALLATION OF OIL PRESSURE SENDERS.
1.
Apply thread sealant tape (3M - Teflon 48 x 1/4”) to the male threads of the sensors being careful not to cover the first three threads.
2.
Remove the protective cover from the fitting and screw the unit into the manifold.
3.
Reconnect the electrical leads to the unit.
4.
Perform an operational check of the system.
— Note —
Refer to Chapter 91 for Electrical Schematics.
ENGINE OIL PRESSURE GAUGE.
The oil pressure gauges are mounted in adjacent configuration on the instrument panel. Each gauge indicates the amount of oil pressure available at the pressurized engine oil passage through a sender at the firewall.
— Note —
The needle of each gauge should be centered +1/2 a needle width on the dot with electric power off. With positive 14 VDC applied to the electrical bus, each gauge should iondicate 0 psi +1 needle width.
79-30-00 Page 79-6 Issued: April 1, 1997
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TROUBLESHOOTING PRESSURE GAUGE.
CHART 7902. OIL PRESSURE GAUGE (TROUBLESHOOTING)
Trouble Cause Remedy
Excessive error at zero. Pointer loose on shaft. Overpressure or seasoning of burdon tube. Repalce instrument.
Excessive scale error. Improper calibration adjustment. Replace instrument.
Excessive pointer oscillation. Air in line or rough engine relief. Disconnect line and fill with light oil. Check for leaks. If trouble persists, clean and adjust relief valve.
Sluggish operation of pointer or pressure fails to build up. Engine relief valve open. Line restriction to instrument. Loss of oil in engine or other engine failure. Clean and check. Clean and check. Shut down engine.
— Note — Gauge will take longer to indicate in cold weather.
REMOVAL AND REPLACEMENT.
Refer to the General sectrion of Chapter 77 for Removal of Cluster Mounted Instruments.
OIL PRESSURE GAUGE CALIBRATION.
A calibration chart has been included for use in verifing that the suspected faulty gauge is within tolerance. Actual recalibration of the gauge must be performed by the manufacturer or an approved instrument repair facility.
1.
With the instrument installed in the aircraft, the aircraft's power connected (14 VDC) and the ground connected.
2.
Remove the connection to the terminal marked SEND and connect a specified amount of resistance as indicated on the chart, by use of a fixed resistor or a test unit capable of simulating the resistance indicated on the chart (Power Resistor Decade Box).
79-30-00 Page 79-7 Issued: April 1, 1997
OIL PRESSURE GAUGE CALIBRATION. (cont)
3.
If the gauge does not meet the tolerances set forth in the chart, it must be replaced or recalibrated.
4.
Reinstallation should be the reverse of the procedure used to disconnect it.
— Note — To facilitate installation, mark or label all wires prior to removal.
GRADUATION CALIBRATION CHART OHMS DEGREES TOLERANCE*
DOT 0# 25# 55# 95# 115# MECH ZERO -40° 10 -34.5° 45 -16° 84.5 +8.5° 132 +27.5° 153 +32° ± 1/2 ± 1/2 ± 1 ± 1 ± 1 +1, -0
* NOTE: TOLERANCES IS IN POINTER WIDTHS
USE 14 VDC
USE WITH ROCHESTER GAUGE 3060-18 SENDER (“K” CURVE) WHITE
Figure 79-1. Oil Pressure Gauge Calibration
79-30-00 Page 79-8 Issued: April 1, 1997
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OIL TEMPERATURE GAUGE.
The oil temperature indicators are mounted in adjacent configuration on the instrument panel. These instruments provide temperature indication of the engine oil in degrees Fahrenheit. The instruments have a temperature bulb located in the oil screen assembly, in the engine accessory section.
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