Service manual

9
CAPACITOR
OHM METER
HIGH LOW
OK
Indicator sweeps back and forth
as shown above. Capacitor is good.
HIGH LOW
OPEN
Indicator shows no movement.
Needle stays to the left side. If needle
shows no movement after reversing the
leads, the capacitor is open.
HIGH LOW
SHORT
Indicator moves to the right side
of the scale and stays there
(indicating a completed circuit).
The capacitor is shorted.
9. Run Capacitors
The purpose of the run capacitors is to give the motors
starting torque and to maintain high power factor during
running. The run capacitors are always connected between
the start and run or main terminals of the motor.
On some older models, one of the terminals of the run
capacitors will have a red dot (the identified terminal). The
identified terminal should always be connected to the run or
main terminal of the motor and to the neutral line.
CAPACITORS
Capacitor Check
There are several capacitor test devices available. The ohm
meter is one of them. The ohm meter cannot verify a
capacitors MFD (microfarrad) value. However, the following
procedures will show you how to use an ohm meter to
determine if the capacitor is good, open, shorted or grounded.
Before testing any capacitor, always perform the following
procedure:
* This test must be done with a analog type meter.
a) Disconnect all electrical power to the air conditioner.
b) Discharge the capacitor with a 20,000 ohm (approx.
3 watt) resistor or larger.
c) You may discharge capacitors with a standard volt
meter if you use a scale over 500 volts and touch the
leads (one lead to each side of the capacitor). The
volt meter will discharge the capacitor.
d) Identify and disconnect the wiring from the
capacitor.
e) Set and zero the ohm meter on the “highest” scale.
When testing for a good, open or shorted capacitor,
perform the following checks: Place the ohm meter
leads across the capacitor terminals (one lead on
each terminal) and perform a continuity test. Then
observe the action of the meter needle or indicator.
Reverse the leads and test again. The result should
be the same. Note: If the capacitor had not been
properly discharged, a false reading could be
indicated on the first test. Always test several times
(reversing the leads with each test). This will verify
the capacitors condition.
Good Capacitor
If the capacitor is good, the indicator will move from infinity
(the left side), towards zero ohms and slowly return back to
infinity. Reverse the leads and test again. The result should
be the same.
Open Capacitor
If the capacitor is open, the indicator will show no deflection
or movement. Reverse the leads and test again. If there is no
indicator movement on the second test, the capacitor is open.
Open capacitors are defective and must be replaced.
Shorted Capacitor
If the capacitor is shorted, the indicator will move towards and sometimes hit zero
ohms, and will stay there. This indicates a completed circuit through the inside of
the capacitor (shorted). Shorted capacitors are defective and must be replaced.