Tecumseh AH5540E, Service Handbook

Page: 73 / 120

65
Step 1: Before Continuing with Troubleshooting
WARNING! All 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 40-41).
You should have also checked the windings for continuity and proper
resistance (see “Checking for Continuity and Proper Resistance” on page 42, made sure
the system is getting proper voltage, and that the control, thermostat, and contactor are
working properly.
NOTE: the compressor housing MUST be at 130°F or less for the following checks. This
temperature can be read by Tempstik or is that temperature which will allow the hand to
remain in contact with the compressor housing without discomfort.
Step 2: Check Internal Thermal Protector
If there is continuity between all terminals the thermal protector should be good. If R to S
has continuity and R to C and S to C do not, the thermal protector may be tripped. Wait
for the protector to cool off and close. This may take more than an hour. Check continuity
gain. If there is no continuity, replace the compressor.
Step 3: Check Run Capacitor
CAUTION: using a 20,000 ohm resistor, discharge the capacitor before removing it from
the system to avoid damage to measuring devices and risk of electric shock. Disconnect
the run capacitor from the system. Use a capacitance meter to check capacitor. Capaci-
tance should be 10% of the marked capacitor value.
As an alternative, check the run capacitor by measuring continuity across the capacitor
terminals:
• Rx1 scale: If there is continuity, then the run capacitor is shorted and needs to be
replaced.
• Rx100,000 scale: If there is no needle deflection on an analog meter or if a digital meter
indicates infinite resistance, 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 100% of rated voltage).
Step 4: Reconnect Run Capacitor
Reconnect the run capacitor into circuit at terminals S and R. (Marked terminal should go
to R.)
Step 5: Continue Troubleshooting
If all above tests prove satisfactory and unit still fails to operate properly, check for ad-
equate compressor pumping as outlined in the procedure on page 70.