Piper Arrow IV, Maintenance Manual

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F. When testing leads which are installed on an engine, it may be found that distributed capacitance
causes the tester to reject good leads if the tester and red test lead are allowed to lay in close
physical contact with the engine parts. For best results, keep the tester and the red high voltage
lead well clear of the grounded metal parts of the engine.
G. On some engines, leakage through the magneto distributor to the magneto coil may occur if the
distributor finger electrode is lined up with the lead undertest. lf this occurs, the tester will indicate
a rejection. Before final rejection of a lead which has one end connected to the magneto, turn the
engine slightly and repeat test to confirm the reading.
6. A second acceptable method for performing an insulation check is with a high voltage, direct current
tester such as the TAKK Model 86 or 86A or an equivalent direct current tester capable of delivering a test
potential of 10,000 volts. Connect ground lead of high voltage tester to outer shielding braid of a single lead.
Connect plug terminal. Turn tester ON and apply 10,000 volts. The insulation resistance should be 100
megohms minimum. Proceed to check other leads of harness in the same manner.
REMOVAL OF HARNESS.
1. Disconnect the clamps that secure the wires to the engine and accessories.
2. Loosen the coupling nuts at the spark plugs and remove the insulators from the spark plug barrel well.
Use caution when withdrawing the insulator so that the insulator spring will not be damaged.
3. Place a guard over the harness insulators.
4. Remove the harness assembly terminal plate from the magneto.
5. Remove the harness from the airplane.
Figure 74-11. Removing Spring From Lead Assembly
Effectivity
PA-28RT-201T
74-21-01
Page 74-11
December 1, 1978
3D20
PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL