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GSH13 - Outdoor Unit Making Humming Noise

Article ID: 570
Last updated: 16 Nov, 2018

Heat Pump: GSH13

Re: Making Humming Noise

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

Qty Possible Causes:
1 Bad Capacitor
1 Locked-Up Compressor
Bad Fan Motor
Low Line Voltage
Burnt Wires
Bad Contactor
Defrost Mode

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.

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
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Article ID: 570
Last updated: 16 Nov, 2018
Revision: 3
Views: 25
Comments: 0