545
Feb 20/85 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 79-33-0 Page 101
LOW OIL PRESSURE WARNING SYSTEM - ADJUSTMENT/TEST
1. Low Oil Pressure Warning System Test
A. General
(1) The low oil pressure warning system can be tested by two different methods. When an engine is started or shut down, the warning light and low oil pressure switch operation may be checked against the oil pressure indicator on the engine instrument panel. The system may also be tested with the engine inoperative by applying an air pressure source to the low oil pressure switch and observing the warning light operation.
B. Equipment and Materials
(1) Variable air pressure source - 38 psi minimum pressure
C. Test Low Oil Pressure Warning System During Engine Start and Shutdown
(1)
With Sec 2 and Sec 5 circuit breakers on panel P6 closed, determine that warning light is illuminated before starting engine.
(2)
During engine start, note pressure at which warning light goes out. Light should go out with increasing pressure before or at 38 psi.
(3)
When engine is shut down, note pressure at which warning light illuminates. Light should come on with decreasing pressure before or when 34 psi is reached.
D. Test Low Oil Pressure Warning System Using Air Pressure Source
(1)
Open left cowl panel to expose left side of engine.
(2)
With external power applied to airplane and Sec 2 and Sec 5 circuit breakers on circuit breaker panel P6 closed, determine that warning light is illuminated before connecting air source.
(3)
Disconnect low oil pressure switch pressure line at banjo fitting in low oil pressure switch OIL port and connect air pressure source to banjo fitting. (See figure 501.)
(4)
Gradually apply air pressure to low oil pressure switch. Warning light should go out with increasing pressure before or at 38 psi.
(5)
Gradually reduce pressure until pressure warning light illuminates. Light should come on with decreasing pressure before or when 34 psi is reached.
(6)
Open Sec 2 and Sec 5 circuit breakers. Light should go out. Close circuit breakers.
(7)
Reduce air pressure to zero psig and remove air pressure source.
(8)
Connect low oil pressure switch pressure line to low oil pressure switch banjo fitting. Do not tighten connection.
(9)
Motor or operate engine until oil leakage is observed at switch pressure line connection. Tighten fitting and install lockwire.
(10)
Close cowl panels.
(11)
If no longer required, disconnect external electrical power (Refer to Chap 24).
CAUTION: DO NOT OVERPRESSURIZE LOW OIL PRESSURE SWITCH OR DAMAGE TO UNIT MAY OCCUR.
500
Aug 15/67 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 79-33-0 Page 501
H31462
Low Oil Pressure Indicating System Test 545
79-33-0 Figure 501 Feb 20/85
Page 502
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
LOW OIL PRESSURE SWITCH - REMOVAL/INSTALLATION
1. Prepare to Remove Low Oil Pressure Switch
A. Open applicable left cowl panel.
B. Open Sec 2 and Sec 5 circuit breakers on circuit breaker panel P6.
2. Remove Low Oil Pressure Switch
A. Remove electrical connector from low oil pressure switch (Fig. 401).
B. Remove vent plug in VENT port and save for new switch.
C. Disconnect low oil pressure switch pressure line and oil pressure transmitter pressure line at banjo fitting in switch OIL port.
D. Remove two bracket mounting screws and remove bracket and switch assembly.
E. If switch is to be replaced with a new unit remove universal bolt and banjo fitting.
3. Install Low Oil Pressure Switch
A. If a new switch is being installed, position banjo fitting in switch OIL port. Install universal bolt thru banjo fitting using new 0-rings, (two for each bolt).
NOTE: Lubricate O-rings with engine oil before installation.
B. To provide adequate electrical bonding, ensure that faying surface between switch mounting base and bracket on engine flange E is clean. Secure switch to bracket using two screws, washers and nuts (Fig. 401).
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