GSH13 - Outdoor Unit Making Humming Noise

Heat Pump: GSH13

Re: Making Humming Noise

When the unit is operating in heating or cooling it makes a loud humming noise.

CHECKOUT:

1. Check Power

• Disconnect power to the outdoor unit by pulling the service disconnect.
• Remove the outdoor unit electrical access panel.
• Look for any signs of burnt wires or controls.
• Re-apply power to the unit by re-inserting the service disconnect plug.
• Check for 230VAC power entering the contactor.
  • Low Voltage ⇒ Check Service Disconnect and Breaker
  • Power Present → Step 2. Check Capacitor

2. Check Capacitor

• Remove power to the unit by pulling the service disconnect.
• Discharge the capacitor by shorting the terminals with a screw driver.
• Compressor
• At the capacitor, remove the wires attached to "C" and "HERM".
• Move Multi-Meter leads to COM and MFD.
• Set Meter to 200 MFD.
• Place one meter lead on "C" and the other on "HERM". 
• Confirm MFD reading with capacitor rating.
  • Less than 80% of rating = Bad Capacitor
• Fan
• At the capacitor, remove the wires attached to "C" and "FAN".
• Place one meter lead on "C" and the other on "FAN". 
• Confirm MFD reading with capacitor rating.
  • Less than 80% of rating = Bad Capacitor
• SWITCH METER LEADS BACK TO COM AND V BEFORE PROCEEDING!

3. Check Unit Operation

• Attach an Amp Probe to one of the inlet power wires.
• Re-apply power to the unit.
• If necessary, energize the contactor by setting the thermostat to call for either heating or cooling (or manually push-in the contactor).
• Watch unit amperage and confirm that the compressor and condenser fan start.
  • Excessive Amperage → Step 4. Check Compressor
  • Outdoor Fan Doesn't Start ⇒ Check outlet voltage at contactor with contactor energized.
    • No or Low Voltage = Bad Contactor

4. Check Compressor 

• Remove power from the unit by pulling the service disconnect.
• Remove the compressor "Common" wire, either at the contactor or at the compressor.
• Check resistance of the compressor windings from "Common" to "Start" and "Common" to "Run".
  • Resistance Between Each Winding + Excessive Start Amperage ⇒ Install a Hard Start and Re-check amperage.
    • Still Won't Start/Excessive Amperage = Locked-Up Comnpressor
  • No Resistance on Either Winding = Burnt Compressor Terminal or Open Compressor Windings 

5. Check Condenser Fan

• Manually spin the condenser fan blade.
  • Won't Spin/Difficult to Spin = Bad Fan Motor ⇒ Check to see if motor has oil ports.
  • Turns Freely + Won't start ⇒ Check voltage to the motor with contactor energized.
    • No Power = Bad Contactor or In Defrost Mode
    • Power + No Operation = Bad Fan Motor