5. With alternator turning at sufficient rpm to produce a half load condition, or approximately 25 amperes
output, voltmeter should read between l3.6 and 14.3-volts.
6. The voltage regulator heat sink, or case, is the ground connection for the electronic circuit. If this unit
is tested on the bench, a wire, No. l4, must be connected between the regulator case and the alternator.
If the regulator does not regulate between l3.6 and l4.4-volts, one of the following conditions may
exist:
a. Regulates, but out of specification. Regulator is out of calibration and must be replaced.
—NOTE—
The 68804-3 (Lamar) regulator has a black ground wire that
must have a low resistance connection to the ground system. It is
adjustable and should be set to 14.0-volts.
b. Voltmeter continues to read battery voltage.
(l) Poor or open connections within wiring harness.
(2) Regulator is open.
c. Voltage continues to rise.
(l) Regulator housing not grounded.
(2) Regulator shorted, must be replaced.
7. These are some things to look for in case of failure:
a. Poor or loose connections.
b. Poor ground on regulator housing.
c. Shorted alternator windings.
d. A grounded yellow wire. (This will cause instantaneous failure.)
e. Disconnecting regulator while circuit is energized.
f. Open circuit operation of alternator (battery disconnected).
CHECKING OVERVOLTAGE RELAY
Test overvoltage relay with a voltmeter, with a scale of at least 20-volts and a suitable power supply, with
an output of at least 20-volts, or sufficient batteries with a voltage divider to regulate voltage. Connect test
equipment as follows:
1. Connect B+ to Bat of overvoltage control.
2. Connect B- to frame of overvoltage control.
3. Be sure both connections are secure, and connected to a clean, bright surface.
4. Connect positive lead of voltmeter to Bat terminal of overvoltage control.
5. Connect negative lead of voltmeter to frame of overvoltage control.
6. The overvoltage control is set to operate between 16.2-volts to l7.3-volts. By adjusting voltage, an
audible click may be heard when relay operates.
7. If overvoltage control does not operate between l6.2 and l7.3-volts, it must be replaced.
EXTERNAL POWER
OPERATION OF EXTERNAL POWER RECEPTACLE
The external power receptacle is located on the right side of the fuselage aft of the wing. When using
external power for starting or operation of any of the airplane’s equipment, proceed as follows:
1. Turn aircraft MASTER SWITCH to OFF position and turn off all electrical equipment.
2. Ensure that red lead of Piper External Power (PEP) kit jumper cable is connected to positive (+)
terminal of external l2-volt battery and that black lead is connected to negative (-) terminal
24 - 41 - 00
Page - 24 - 40
Reissued: August 1, 1986
1J15
PIPER AIRCRAFT
PA-28-236
MAINTENANCE MANUAL
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