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Current --
For the current type, contacts are normally open. The start contacts close by the high current draw from the
locked rotor condition with only the run winding in the circuit. As the contacts close, the start capacitor and the
start winding is energized and the compressor starts. At approximately 80% of its operating speed the current
draw drops off, the relay contacts open removing the start winding and start capacitor from the circuit. Remem-
ber, current relays are directional in their mounting to allow contacts to lift and close.
Capacitors
A quick check is to replace suspected defective capacitors with known good capacitors being careful to stay
within the range for substitute values. Should those values be unknown, a basic rule for capacity is: for start ca-
pacitors
¦
10% and run capacitors
¦
5% of the rating on the defective original capacitor being replaced. Voltage
should always try and be matched; if it cannot be, it is acceptable to increase up to 10% higher than the voltage
listed on the capacitor being replaced. NEVER put a capacitor on a product with a voltage rating lower than the
original being replaced. If a capacitor analyzer is not available, an ohm meter may be used to check a capacitor
for short or open circuits. Set the ohm meter to its highest scale and connect its leads to the capacitor terminals.
1. With a capacitor, without plate defect, the indicator should first move to zero (0) and then gradually in-
crease to infinity.
2. If there is no movement of the ohm meter indicator, an open circuit is indicated.
3. If the ohm meter indicator moves to zero (0) and remains there, or on a low resistance reading, a short cir-
cuit is indicated.
4. Please note this check does not determine if the capacitor will deliver the proper rated MFD/UFD required,
it only shows if the capacitor has shorted or open circuits.
5. Capacitors that show any signs of leakage of electrolyte, or damage of the can, should be replaced. DO
NOT TEST!
Compressor
1. Using an ohm meter, check for continuity from compressor terminal C to R and C to S. If the compressor is
hot, wait one (1) hour for compressor to cool and recheck. An open internal overload protector can cause a
lack of continuity. If continuity cannot be measured through all windings, the compressor must be replaced.
2. To check the compressor motor for accidental ground, perform a continuity check between terminals C, R
and S to the compressor shell or a copper line of the refrigeration system (do not use a painted surface).
Continuity present, the compressor windings are grounded and the compressor must be replaced.
If the compressor starts, but trips repeatedly on the overload protector, remember that the overload is both tem-
perature and current activated. Be sure to check:
S
Low voltage
S
Undersized supply lines
S
High head pressure
S
High suction pressure
S
Defective capacitors
S
Compressor mechanical problems
S
Low refrigerant charge
