GLAS Short Cycling Control or Sensing Issue

Thermostat and HVAC system short cycle: heating or cooling turns on and off rapidly in short bursts.

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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

Incorrect cycle rate or differential settings, Thermostat located near supply vent or return, Oversized HVAC system, Faulty temperature sensor in GLAS

How to Fix / Troubleshooting

Safety: Mostly configuration and placement; minimal electrical work.

  • Step 1 – Check cycle settings: In GLAS settings, adjust any available cycle rate or temperature differential to allow longer run times.
  • Step 2 – Inspect location: Ensure GLAS is not directly in the path of supply air or near a return grille that causes rapid temperature swings.
  • Step 3 – Seal wall cavity: Seal gaps behind the wall plate to prevent drafts from the wall cavity.
  • Step 4 – Monitor behavior: After adjustments, monitor for several hours. If short cycling persists and the furnace or AC is rapidly starting and stopping, contact an HVAC technician to evaluate system sizing and safety controls.
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Repair Difficulty

Medium 3/5

Required Part

GLAS Internal Temperature Sensor Board
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