Specifications

183 Rev. 3
SERVICING
1
2
3
4
5
OHMMETER
TESTING FAN RELAY
S-12 CHECKING HIGH PRESSURE CONTROL
(some models)
The high pressure control capillary senses the pressure in
the compressor discharge line. If abnormally high condens-
ing pressures develop, the contacts of the control open, break-
ing the control circuit before the compressor motor overloads.
This control is manually reset.
WARNING
Disconnect Electrical Power Supply:
1. Using an ohmmeter, check across terminals of high pres-
sure control, with wire removed. If not continuous, the
contacts are open.
2. Reset high pressure control.
3. Attach a gauge to the dill valve port on the base valve.
With power ON:
WARNING
LINE VOLTAGE NOW PRESENT.
4. Start the system and place a piece of cardboard in front
of the condenser coil, raising the condensing pressure.
5. Check pressure at which the high pressure control cuts-
out.
If it cuts-out at 440 PSIG (400 PSIG some models) ± 10
PSIG, it is operating normally (See causes for high head
pressure in Service Problem Analysis Guide). If it cuts out
below this pressure range, replace the control
S-13 CHECKING LOW PRESSURE CONTROL
(some models)
The low pressure control senses the pressure in the suction
line and will open its contacts on a drop in pressure. The low
pressure control will automatically reset itself with a rise in
pressure.
The low pressure control is designed to cut-out (open) at
approximately 35 PSIG. It will automatically cut-in (close) at
approximately 85 PSIG.
Test for continuity using a VOM and if not as above, replace
the control.
S-14 CHECKING SCROLL COMPRESSOR DIS-
CHARGE THERMOSTAT
Phase 1 scroll compressors are equipped with an internal
thermostat located beneath the top cap on the compressor.
This thermostat is designed to sense dangerous discharge
temperatures reached under some extreme operating condi-
tions (such as loss of charge or extremely high compression
ratio).
Is maximum safe operating temperatures are exceeded the
thermostat will open removing power to the compressor. Once
the discharge temperature has cooled the thermostat will close
and normal operation will resume.
WARNING
Disconnect Electrical Power Supply:
1. Check for continuity across the terminals of the com-
pressor thermostat. If continuity is not read the thermo-
stat contacts are open.
2. If the contacts read open, allow the thermostat to cool to
140°F. and retest. If the thermostat continues to read
open it should be replaced.
NOTE: This protective device should never be bypassed for
any purpose.
The approximate thermostat cut-out/cut-in temperatures are
290/140°F.
S-15 CHECKING CAPACITOR
SCROLL COMPRESSOR MODELS
Hard start components are not required on Scroll compres-
sor equipped units due to a non-replaceable check valve lo-
cated in the discharge line of the compressor.