(5)  
Remove oil temperature indicator from engine instrument panel and disconnect electrical connector.

(6)  
Connect electrical connector to test indicator. Temperature reading of test indicator should correspond with temperature reading obtained from airplane indicator in step (3) within士 5oC.

(7)  
Remove electrical connector from test indicator, connect to airplane indicator and install airplane indicator in engine instrument panel.

(8)  
If no longer required, remove external electrical power.

500 
Aug 15/67  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  79-34-11 Page 501 

OIL TEMPERATURE BULB - REMOVAL/INSTALLATION
1.  Remove Oil Temperature Bulb (Fig. 401)
A.  Open left side removable cowl panel.
B.  Open applicable Oil Temperature and Pressure circuit breaker on panel P6.
CAUTION:  FAILURE TO OPEN CIRCUIT BREAKER BEFORE REMOVING OIL TEMPERATURE BULB ELECTRICAL CONNECTOR MAY RESULT IN DAMAGE TO OIL TEMPERATURE INDICATOR.
C.  Disconnect electrical connector from oil temperature bulb located in oil outlet fitting on fuel oil cooler.
D.  Remove oil temperature bulb by unscrewing bulb from fitting.
2.  Install Oil Temperature Bulb
NOTE: Make electrical bond between oil temperature bulb and fuel oil cooler faying surfaces.
Maximum resistance across faying surfaces is 0.0025 ohms (2.5 milliohms).

A.  Install oil temperature bulb in oil outlet fitting on fuel oil cooler and lockwire.
B.  Install electrical connector on oil temperature bulb and lockwire to boss on fuel oil cooler fitting.
C.  Close left side cowl panel.
D.  Close applicable Oil Temperature and Pressure circuit breaker on panel P6.
E.  Operate engine (Ref 71-09-100, MP). Check that oil temperature bulb indications are normal.
500 
Jan 20/83  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  79-34-21 Page 401 

H29449
Oil Temperature Bulb Installation  500 
79-34-21  Figure 401  Aug 15/67 
Page 402 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

OIL FILTER BYPASS WARNING SYSTEM - DESCRIPTION AND OPERATION
1. General
A.  The oil filter bypass warning system provides indication in the control cabin of an engine oil filter bypass valve about to bypass oil around a clogged filter. The system consists of two amber lights on the center instrument panel and an oil filter bypass switch mounted on each engine Fig. 1).
B.  The oil filter bypass switch senses the oil pressure on each side of the engine main oil filter. An increase in pressure difference across the filter closes the switch and completes a 28 volt dc circuit to illuminate the amber filter bypass light on the center instrument panel.
2.  Oil Filter Bypass Switch
A.  The oil filter bypass switch is a pressure operated switch which senses the oil pressure drop across the engine oil filter. The switch is designed to operate at a differential pressure of 34 to 38 psi.
B.  The oil filter bypass switch is mounted on a bracket attached to the accessory drive gearcase at approximately the 7 o'clock position just above the gearcase overboard breather. On some engines the oil filter bypass switch is mounted on a bracket attached to the constant speed drive oil filter on the left side of the engine (Fig. 1).
3.  Oil Filter Bypass Warning Light
A.  The oil filter bypass warning light is a press-to-test type light that is connected to the airplane master test and master dim switches. The light for each engine is located on the upper right portion of the center instrument panel.
4.  Operation
A.  During engine operation the main oil filter may become clogged. If the filter becomes sufficiently contaminated to impede the supply of oil to the bearings, a bypass valve in the filter will open diverting the oil past the filter and providing an uninterrupted oil supply to the bearings. At an oil pressure differential of approximately 34 to 38 psi between the inlet and outlet of the filter, the switch will close illuminating the warning light. Illumination of the warning light is designed to precede actual bypass of the oil filter.
504 
May 20/82  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  79-35-0 Page 1 

H27810
Oil filter Bypass Warning System  504 
79-35-0  Figure 1  May 20/82 
Page 2 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

OIL FILTER BYPASS WARNING SYSTEM - TROUBLE SHOOTING
　
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