Tecumseh AH5540E - Page 59

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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.
Step 2: Disconnect Fan Motor or Any Other Devices
If there is a fan motor or any other auxiliary device, open the circuit for the fan motor or any
other device.
Step 3: Check External Thermal Protector
Check for continuity across the thermal protector (line 1 and compressor terminal con-
nection). If there is no continuity then 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 protector.
Step 4: Check Current Relay
Keep the relay upright. Check the relay by measuring continuity between:
Relay terminals 1 and S. If there is continuity, then the relay contacts are closed when they
should be open. Replace the current relay.
Relay terminals 2 and M. If there is no continuity, replace the current relay.
Step 5: Check Start 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 start capacitor from the system. Use a capacitance meter to measure the capacitance.
The capacitance value should be the rated value minus 0% to plus 20%. If it is outside of
this range, then the start capacitor needs to be replaced.
As an alternative, check the start capacitor by measuring continuity across capacitor ter-
minals:
• Rx1 scale: If there is continuity, then the start 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 start capacitor is open and needs to be
replaced.
Possible reasons that a start capacitor is not working properly include:
• Use of incorrect start capacitor. Replace with proper start capacitor.
• The relay contacts are not working properly. Replace the relay.
• Prolonged operation on start cycle due to low voltage. Determine if the line voltage
is too low (less than 90% of rated voltage).
• Prolonged operation on start cycle due to incorrect relay. Replace with correct
relay.