Tecumseh AH5540E Service Handbook page 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.
Step 2: Check Potential Relay
Before checking the relay, be sure it is mounted at the proper position (see pages 21-23).
Check the potential relay by measuring continuity between:
• Relay terminals 5 and 2. If there is no continuity, replace the relay.
• Relay terminals 2 and 1. If there is no continuity, then the contacts are open. Replace
the relay.
Possible reasons that a relay is not working properly include:
• Use of incorrect relay. Replace with correct relay.
• Line voltage is too high or low (greater than 110% or less than 90% of rated voltage).
• Excessive short cycling. Short cycling can be caused by problems with the com-
pressor's thermal protector or system components such as the thermostat, control,
contactor, or high or low pressure cut-out. For more information on troubleshooting
the thermal protector, see Step 5. For troubleshooting the system components, refer
to the OEM service information.
• Vibration due to loose relay mounting. Tighten relay mounting.
• Use of incorrect run capacitor. Replace with proper run capacitor.
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: 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.
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