Electrical Power Supply; Inspection Of Magneto - Piper Dakota Maintenance Manual

ELECTRICAL POWER SUPPLY

MAGNETO
INSPECTION OF MAGNETO (Refer to Piper Vendor Service Publication 61.)
After first 50 hour period and every 100 hours thereafter, check the magneto ignition system. If engine
develops operating troubles which appear to be caused by the ignition system, check the spark plugs and
wiring first before working on the magneto. If trouble appears definitely associated with the magneto, the most
effective measure is to install a replacement magneto, and send the suspected unit to an overhaul shop for test
and repair. If this is not possible, visually inspect the following:
1. Check lead terminals for definite contact with spring contacts in outlets.
2. Remove harness outlet cover from magneto and inspect for presence of moisture and carbon tracking
due to moisture.
3. Check contact springs in distributor block for evidence of spark erosion.
4. Check height of contact springs (0.422 maximum from top of block tower to spring). (Refer to figure
74-1.)
5. With cover and harness separated from magneto housing, check contact assemblies to see that cam
follower is securely riveted to its spring.
6. Examine contact points for excessive wear or burning. (Refer to figure 74-2.)
Do not open point contacts more than 0.0625 of an inch for
examination of contact surfaces. Excessive spreading of breaker
points will overstress and damage contact spring.
The desired contact surface has a dull gray, sand-blasted (almost rough) or frosted appearance. This shows
that points are worn in and mated to each other, providing the best possible electrical contact and most efficient
performance. Minor irregularities or roughness of point surfaces are not harmful. (Refer to figure 74-2, center.)
If there is a possibility of pit becoming deep enough to penetrate pad (refer to figure 74-2, right), reject contact
assembly.
No attempt should be made to stone or dress contact points.
Should contact assembly have bad points or show excessive wear,
complete contact assembly should be replaced.
7. Check condition of cam follower felts for proper lubrication. If oil has seeped from one follower felt to
another, it may be necessary to remove lubrication from one felt strip while oiling another. If felt is
overlubricated, remove oil with a clean, lintless cloth. If dry, apply one or two drops of Bendix
Breaker Felt Lubricant 10-86527.
PIPER AIRCRAFT
PA-28-236
MAINTENANCE MANUAL
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74 - 11 - 00
Page - 74-03
Reissued: August 1, 1986