Heil / Tempstar / Comfortmaker / KeepRite (ICP) · Furnace error code

5 flashesFlame sensed with gas valve off

Cross-checked Licensed pro only

Unlock what this code means, its causes, tests and parts

Full library + AI assistant for $34.90, one time.

Stop: this involves gas or the sealed refrigerant system.

OnCall Tech only describes the symptom. Gas work needs a licensed gas technician, and refrigerant work requires EPA Section 608 certification. If you smell gas: shut off the supply if it is safe, do not switch anything on or off, ventilate, leave the building and call the gas utility.

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

Related diagnostic guides

Guide · Furnace

Igniter glows but burners never light

If the igniter glows and no flame appears, the problem is on the gas side (supply off, valve not opening, valve not receiving 24 V). You can confirm the gas shutoff is open and whether the board sends the valve signal; the valve and gas pressure are licensed-technician work.

3 steps ~30 minadvanced

Guide · Furnace

Furnace runs no heat (blower only or nothing)

Start with the board LED code, then work the call path: thermostat, 24 V, safeties, inducer, ignition, flame proving. Most no-heat calls end at a filter, a flame sensor, a pressure switch issue or gas being off.

5 steps ~45 minmoderate

Guide · Furnace

Known issue: Trane / American Standard 4YCZ5 gas/electric packaged units, gas valve can open (2025 recall)

In July 2025 Trane Technologies and the CPSC recalled about 4,790 two-stage gas/electric packaged units (models 4YCZ5024F1060A, 4YCZ5036F1070A, 4YCZ5036F1090A, 4YCZ5048E1090A, 4YCZ5048E1115A, specific serial ranges, sold January 2024 to March 2025) because the gas valve could open unexpectedly. Owners were told to stop using heating mode; the installing dealer inspects and replaces the ignition board free. Serial ranges differ slightly between notices, so confirm with Trane.

6 steps ~20 mineasy