SERVICING
24
S-1 CHECKING VOLTAGE
WARNING
1. Remove doors, control panel cover, etc. from unit being
tested.
With power ON:
WARNING
LINE VOLTAGE NOW PRESENT.
2. Using a voltmeter, measure the voltage across terminals
L1 and L2 of the contactor for single phase units, and L3,
for 3 phase units.
3. No reading - indicates open wiring, open fuse(s) no power
or etc. from unit to fused disconnect service. Repair as
needed.
4. With ample voltage at line voltage connectors, energize
the unit.
5. Measure the voltage with the unit starting and operating,
and determine the unit Locked Rotor Voltage.
Locked Rotor Voltage
is the actual voltage available at
the compressor during starting, locked rotor, or a stalled
condition. Measured voltage should be above minimum
listed in chart below.
To measure Locked Rotor Voltage attach a voltmeter to
the run "R" and common "C" terminals of the compres-
sor, or to the T
1
and T
2
terminals of the contactor. Start
the unit and allow the compressor to run for several sec-
onds, then shut down the unit. Immediately attempt to
restart the unit while measuring the Locked Rotor Volt-
age.
6. Should read within the voltage tabulation as shown. If
the voltage falls below the minimum voltage, check the
line wire size. Long runs of undersized wire can cause
low voltage. If wire size is adequate, notify the local
power company in regards to either low or high voltage.
Voltage
Min.
Max.
460
437
506
208/230
198
253
Unit Supply Voltage
S-2 CHECKING WIRING
WARNING
1. Check wiring visually for signs of overheating, damaged
insulation and loose connections.
2. Use an ohmmeter to check continuity of any suspected
open wires.
3. If any wires must be replaced, replace with comparable
gauge and insulation thickness.
S-3 CHECKING THERMOSTAT, WIRING, AND
ANTICIPATOR
S-3A THERMOSTAT AND WIRING
WARNING
LINE VOLTAGE NOW PRESENT.
With power ON and thermostat calling for cooling.
1. Use a voltmeter to verify 24 volts present at thermostat
wires C and R.
2. If no voltage present, check transformer and transformer
wiring. If 24 volts present, proceed to step 3.
3. Use a voltmeter to check for 24 volts at thermostat wires C
and Y.
4. No voltage indicates trouble in the thermostat, wiring or
external transformer source.
5. Check the continuity of the thermostat and wiring. Repair
or replace as necessary.
INDOOR BLOWER MOTOR
With power ON:
WARNING
LINE VOLTAGE NOW PRESENT.
1. Use a voltmeter to verify 24 volts present at thermostat
wires C and R.
2. If no voltage present, check transformer and transformer
wiring. If 24 volts present, proceed to step 3.
