A continuity test measures whether electrical current can flow unobstructed through a component or circuit using a digital multimeter. This fundamental diagnostic procedure verifies that switches, solenoids, capacitors, relays, and wiring have no breaks or excessive resistance that would prevent operation. Continuity tests read “0 ohms” for good connections and show “open” for breaks.
Testing Procedure
Technicians disconnect power, set the multimeter to ohms mode, and touch probes across the component being tested. A capacitor should show infinite resistance (open) unless it has a bleeder resistor rated at 50 kilohms or higher. Coil windings typically measure 5-20 ohms depending on wire gauge and length.
Common Applications
Continuity testing diagnoses thermostat failures, contactor problems, blower motor issues, and control circuit breaks. Testing capacitors for leakage and determining if a compressor’s thermal overload has opened are routine procedures. This test is essential before replacing expensive components, saving time and cost in HVAC troubleshooting.