S001
GLAS System Detection / Configuration Error

Thermostat displays S001 and cannot detect the type of HVAC system connected; setup wizard cannot complete.

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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 or incomplete wiring at GLAS wall plate, Unsupported multi‑stage or accessory configuration, Loose wall plate connection to GLAS body, Firmware bug in auto‑detection routine

How to Fix / Troubleshooting

Safety: Turn off power to HVAC equipment at the breaker before changing wiring.

  • Step 1 – Verify wiring against GLAS manual: Compare your current wiring to the GLAS installation guide for your system type (conventional furnace/AC vs. heat pump). Correct any miswired or unused terminals.
  • Step 2 – Ensure minimum required wires: For most systems, GLAS needs at least R, C, and W (heat) or Y (cool). Add a C‑wire if missing.
  • Step 3 – Reseat thermostat: Remove GLAS from the wall plate and reattach firmly to ensure all pogo‑pin contacts are engaged.
  • Step 4 – Manual configuration: In the setup wizard, choose manual system configuration instead of auto‑detect and specify your system type and stages.
  • Step 5 – Firmware update: If possible, update GLAS firmware and retry setup.
  • Step 6 – Replace thermostat: If S001 persists with correct wiring and configuration, the wall plate connector or main board may be defective. Replace the GLAS thermostat and wall plate.
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Repair Difficulty

Medium 3/5

Required Part

GLAS Wall Plate Connector Assembly
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