How to test continuity of the Trane AC compressor?

 
Safety First
 

At Hoffman Brothers, we prioritize your safety—ensuring that every precaution is taken for our clients in St. Louis.

 

• Disconnect all power sources to the HVAC unit to prevent electrical shock or damage to equipment.
• Wear insulated gloves and eye protection as an extra precaution.
• Make sure that the area is dry and that you have a clear working space.

 
Gathering Tools and Equipment
 

• Obtain a digital multimeter that can measure resistance (ohms) and continuity.
• Have insulated screwdrivers, pliers, and any necessary tools to access the compressor’s wiring terminals.
• Refer to the unit’s wiring diagram to identify the compressor terminals accurately.

 
Isolating the Compressor
 

• Remove or disconnect the wiring harnesses connected to the Trane AC compressor to isolate it from the circuit.
• Ensure that the compressor is completely disconnected to avoid interference from parallel circuits.
• Label wires if necessary to ensure correct reconnection later.

 
Setting Up the Multimeter
 

• Turn the multimeter dial to the ohms (Ω) setting, or the continuity mode if available.
• If using the continuity mode, the meter will typically emit a beep when a continuous circuit is detected.
• Calibrate the multimeter if needed, following the manufacturer’s instructions.

 
Identifying Compressor Terminals
 

• Locate the compressor’s electrical terminals based on the wiring diagram. Common terminals include start winding, run winding, and ground.
• Check the compressor’s label or manual for specific terminal designations.
• Be aware that some compressors have an integrated start relay or capacitor; ensure you understand the connections.

 
Performing the Continuity Test
 

• Place one probe of the multimeter on one of the compressor’s terminals (for example, the start winding).
• Touch the other probe to the corresponding terminal (such as the run winding) as indicated by the wiring diagram.
• Observe the meter reading:
  • If using the ohms setting, a low resistance value (typically a few ohms) indicates continuity.
  • If using the continuity setting, a beep confirms a continuous circuit.
• If the reading is infinite (open circuit) or the meter does not beep in continuity mode, the winding may be faulty.

 
Checking for Shorts to Ground
 

• Test each terminal by placing one probe on the terminal and the other on the compressor’s metal body or designated ground point.
• A low resistance or audible beep in continuity mode in this test could indicate a short circuit, which is a critical fault.
• No continuity (i.e., high/infinite resistance) between the winding and ground is expected under normal conditions.

 
Interpreting the Results
 

• Normal readings: A low resistance value between the appropriate terminals confirms that the windings are intact and continuous.
• Open circuits: An infinite reading between terminals indicates that the circuit is broken and the winding needs checking or replacement.
• Short circuits: A low-resistance measurement between any winding and ground indicates that there is a short, which is hazardous and requires immediate attention.

 
Post-Test Procedures
 

• Reassemble any components or wiring that were disconnected during testing once you have completed your checks.
• Double-check all connections following the manufacturer's specifications when reactivating the unit.
• Restore power to the HVAC system, and consider a further operational test to ensure that the system runs properly.

For reliable HVAC service and repairs, residents and businesses in St. Louis trust Hoffman Brothers to deliver exceptional quality and care.