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Single Phase Resistance Test
Remove the leads from the compressor terminals and set
the ohmmeter on the lowest scale (R x 1).
Touch the leads of the ohmmeter from terminals common
to start (“C” to “S”). Next, touch the leads of the ohmmeter
from terminals common to run (“C” to “R”).
Add values “C” to “S” and “C” to “R” together and
check resistance from start to run terminals (“S” to “R”).
Resistance “S” to “R” should equal the total of “C” to “S”
and “C” to “R.”
In a single phase PSC compressor motor, the highest
value will be from the start to the run connections (“S” to
“R”). The next highest resistance is from the start to the
common connections (“S” to “C”). The lowest resistance
is from the run to common. (“C” to “R”) Before replacing a
compressor, check to be sure it is defective.
GROUND TEST
Use an ohmmeter set on its highest scale. Touch one
lead to the compressor body (clean point of contact as
a good connection is a must) and the other probe in turn
to each compressor terminal. If a reading is obtained the
compressor is grounded and must be replaced.
Check the complete electrical system to the compressor
and compressor internal electrical system, check to be
certain that compressor is not out on internal overload.
Complete evaluation of the system must be made
whenever you suspect the compressor is defective. If
the compressor has been operating for sometime, a
careful examination must be made to determine why the
compressor failed.
Many compressor failures are caused by the following
conditions:
1. Improper air fl ow over the evaporator.
2. Overcharged refrigerant system causing liquid to be
returned to the compressor.
3. Restricted refrigerant system.
4. Lack of lubrication.
5. Liquid refrigerant returning to compressor causing oil
to be washed out of bearings.
6. Noncondensables such as air and moisture in
the system. Moisture is extremely destructive to a
refrigerant system.
7. Defective capacitors.
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