Piper Arrow IV, Maintenance Manual

Page: 615 / 752

ELECTRICAL POWER SUPPLY.
MAGNETOS.
—CAUTION—
Ascertain that the primary circuits of both magnetos are
grounded before working on the engine.
—NOTE—
The magneto service instructions in this manual cover minor
repairs and timing. For further repairs and adjustments of the
magnetos, it is recommended that the magneto manufacturer’s
service instructions be followed.
INSPECTION OF MAGNETOS.
1. After the first 25 hour and 50 hour periods, and periodically thereafter, the contact assemblies should
be checked. Examine the points for excessive wear or burning. Points which have deep pits or excessively
burned areas should be discarded. Examine the cam follower felt for proper lubrication. If necessary, points
can be cleaned by using any hard finished paper. Clean breaker compartment with dry cloth.
2. If engine operating troubles develop which appear to be caused by the ignition system, it is advisable
to check the spark plugs and wiring first before working on the magnetos.
3. Should trouble appear definitely associated with the magneto, the most effective measure is to install a
replacement magneto which is known to be in satisfactory condition and send the suspected unit to the
overhaul shop for test and repair.
4. Should this not be possible, a visual inspection may disclose the source of trouble. Remove the harness
outlet plate from the magneto. Inspect for the presence of moisture and foreign matter on the rubber grommet
and high tension outlet side of the distributor block. Check height of block contact springs. The top of the
spring must not be more than 0.422 of an inch below the top of the tower as shown in Figure 74-2. If the
springs are broken or corroded, replace them.
5. Inspect the distributor block for cracks or burned areas. The wax coating on the block should not be
removed. Do not use solvents.
6. Check for excess oil in the breaker compartment. If present, it may mean a bad oil seal or oil seal
bushing at the drive end. Check the magneto manufacturer’s overhaul procedure.
7. Remove the breaker cover and harness securing screws and nuts and separate cover from magneto
housing. Check contact assemblies to see that cam follower is securely riveted to its spring. Examine the
contact points for excessive wear or burning. Figure 74-3 shows how the average contact point will look when
surfaces are separated for inspection. Desired contact surfaces have a dull gray, sandblasted (almost rough) or
frosted appearance over the area where electrical contact is made. This means that points are worn in and
mated to each other, thereby providing the best possible electrical contact and highest efficiency of
performance.
Effectivity 74-11-01
PA-28RT-201T Page 74-02
December 1, 1978
3D11
PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL