Trane Furnace Error Code 79: How to Fix It

Q: What causes Trane furnace error code 79?

Error code 79 is caused by a failed indoor coil temperature sensor, damaged sensor wiring, poor sensor contact with the coil, or occasionally a faulty control board that can't read the sensor properly.

Q: Can I bypass the temperature sensor temporarily?

No, you should not bypass the indoor coil temperature sensor as it's a critical safety component that prevents the coil from freezing or overheating. Operating without it can cause serious damage to your furnace.

Q: How much does it cost to replace a Trane furnace temperature sensor?

The sensor itself typically costs $20-50, but professional installation can range from $150-300 depending on your location and the complexity of accessing the sensor in your specific furnace model.

Q: How often do furnace temperature sensors need replacement?

Temperature sensors typically last 10-15 years under normal conditions, but can fail sooner due to electrical surges, moisture exposure, or physical damage from maintenance activities.

Q: Will my furnace work with a bad temperature sensor?

Your furnace may run intermittently or not at all with a failed temperature sensor. The system relies on accurate temperature readings to operate safely and efficiently, so it will often shut down to prevent damage when the sensor fails.

Abstract

Trane furnace error code 79 indicates that your indoor coil temperature sensor has failed or is sending incorrect readings to the control board. This sensor monitors the temperature of the evaporator coil to ensure proper heating and cooling operation, and when it malfunctions, your furnace may not heat properly or could shut down completely.