Friedrich 2008 - Manual (Page 21)

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1. With no power to unit, remove the leads from the com-
pressor terminals.
2. Using an ohmmeter, test continuity between terminals
C-S and C-R. If no continuity, the compressor overload
is open and the compressor must be replaced.
CHECKING THE INTERNAL OVERLOAD
INTERNAL OVERLOAD
Some model compressors are equipped with an internal
overload. The overload is embedded in the motor windings
to sense the winding temperature and/or current draw. The
overload is connected in series with the common motor
terminal.
Should the internal temperature and/or current draw become
excessive, the contacts in the overload will open, turning off
the compressor. The overload will automatically reset, but
may require several hours before the heat is dissipated.
Internal Overload
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 flow 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.
ELECTRIC SHOCK HAZARD
WARNING
Disconnect power to the unit before
servicing. Failure to follow this warning
could result in serious injury or death.