A LOOK AT SERVICE SAFETY
Servicing
77
Step 1: Before Continuing with
Troubleshooting...
WARNING!
A
ll electric power should be disconnected and you
should have already made sure that the compressor does not
have a ground fault (see “Checking for a Ground Fault” on
pages 47-48).
You should have also checked the windings for con-
tinuity and proper resistance (see “Checking for Continuity and
Proper Resistance” on pages 48-49), made sure the system is get-
ting proper voltage, and that the control, thermostat, and contac-
tor are working properly.
Step 2: Disconnect Fan Motor or Any
Other Devices
If there is a fan motor or any other auxiliary device, open the cir-
cuit for the fan motor or any other device.
Step 3: Check Run Capacitor
CAUTION:
Using a 20,000 ohm resistor, discharge the capaci-
tor before removing it from the system to avoid damage to mea-
suring devices and risk of electric shock.
Disconnect the run
capacitor from the system. Use a capacitance meter to check
capacitor. Capacitance should be ±10% of the marked capacitor
value.
As an alternative, check the run capacitor by measuring continuity
across the capacitor terminals:
a. Rx1 scale: If there is continuity, then the run capacitor is
shorted and needs to be replaced.
b. Rx100,000 scale: If there is no needle deflection on an
analog meter or if a digital meter indicates infinite resis-
tance, then the run capacitor is open and needs to be
replaced.
Possible reasons that a run capacitor is not working properly
include:
•
Use of incorrect run capacitor. Replace with proper run
capacitor.
•
Line voltage is too high (greater than 110% of rated volt-
age).
Step 4: Check Wired-in PTC Relay
Check the relay by measuring continuity between the pin holes
where the R and S pins on the compressor are inserted. If there is
no continuity, the relay may be open. Wait 3 minutes, then check
continuity again. If there is still no continuity, replace the relay.
Step 5: Check External Thermal
Protector
Check the external thermal protector by measuring continuity
between the power-in terminal and the female C (common) ter-
minal pin. If there is no continuity, the thermal protector may be
tripped. Wait at least 5 minutes, then check continuity again. If
there is still no continuity, replace the thermal protector.
Step 6: Continue Troubleshooting
If all above tests prove satisfactory and unit still fails to operate
properly, check for adequate compressor pumping as outlined in
the procedure on page 83.