Contactor
A contactor is the switch that turns the outdoor AC or heat pump unit on and off.
What Contactor means at home
The contactor receives a low-voltage signal and closes to send high-voltage power to the compressor and outdoor fan. If the contacts are burned, stuck, or not pulling in, the outdoor unit may not start or may not stop when it should — a situation for AC repair or heat pump repair. This is a cabinet-level electrical part, so homeowners should not press or bypass it; contact a qualified technician.
What it connects to
Parent system
the outdoor unit electrical control circuit
Contactor is part of the outdoor unit electrical control circuit. That tells you which side of the system a technician will usually test first.
Related components
thermostat, compressor, condenser fan, capacitor
These are the parts most likely to be checked with contactor. One weak part can make a nearby part look guilty, especially when airflow, water, heat, or controls are involved.
Connected problems
outdoor unit will not start, stuck running, clicking, burned contacts
This is what you are likely to notice at home: outdoor unit will not start, stuck running, clicking, burned contacts. Those clues are more useful than guessing at the failed part.
Maintenance relevance
electrical inspection, contact testing, low-voltage checks, annual tune-ups
This is where electrical inspection, contact testing, low-voltage checks, annual tune-ups matters. The goal is to catch dirt, water, electrical weakness, or airflow strain before the next hard-weather day.
When to call a technician
the outdoor unit clicks without starting or keeps running after the thermostat stops calling
Schedule service when the outdoor unit clicks without starting or keeps running after the thermostat stops calling. At that point the issue usually needs measurements, not another thermostat setting change.
Questions homeowners ask about Contactor
What does contactor mean in HVAC?
A contactor is the switch that turns the outdoor AC or heat pump unit on and off.
Can a homeowner fix a contactor problem?
You can check the thermostat, replace a dirty filter, make sure vents are open, and look for water or ice. Stop before sealed panels, wiring, refrigerant, gas, combustion parts, or safety controls.
When should I call about contactor?
Call when the problem changes comfort, airflow, safety, water, ice, odor, noise, breakers, or how often the system starts and stops. Tell the technician what changed before you try to name the part.