Armstrong Air
Contactor Chatter / Coil Voltage Instability
Loud buzzing or chattering noise from outdoor unit contactor area
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Low 24V control voltage, Loose low-voltage connections, Failing contactor coil, Thermostat or board rapidly cycling Y call
How to Fix / Troubleshooting
Safety first: Turn off power at the disconnect before touching the contactor or wiring.
Steps:
- 1. Inspect low-voltage wires: Tighten the two small-gauge wires on the contactor coil terminals.
- 2. Check for corrosion: Clean any corroded terminals with contact cleaner and a small brush.
- 3. Measure coil voltage: With power on and a call for cooling, a qualified person can measure voltage across the coil. It should be around 24 VAC and stable.
- 4. Replace contactor if needed: If voltage is stable but the contactor still chatters or buzzes loudly, replace it with an Armstrong Air-approved contactor of the same rating.
- 5. If voltage is unstable: The issue may be with the thermostat, indoor board, or transformer and should be evaluated by a technician.
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Repair Difficulty
Medium
3/5
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