TRANE XR90 / XT80 SERIES Flashes Pressure Switch

Furnace Pressure Switch

The internal silicone diaphragm in the pressure switch can fatigue or crack over time, preventing it from closing the electrical circuit even when the inducer motor is running. This part is the primary sensor responsible for the '3-flash' error code when it fails to detect the required vacuum threshold.

Inducer Draft Blower Assembly

If the inducer motor bearings are worn or the fan wheel is obstructed by debris, it cannot generate the necessary cubic feet per minute (CFM) to create a vacuum strong enough to trigger the pressure switch. This assembly is a common failure point that results in insufficient static pressure within the collector box.

Pressure Switch Tubing Kit

Silicone tubing can become brittle or develop hairline cracks due to high thermal cycling inside the furnace cabinet. A breach in the tubing integrity allows atmospheric pressure to bleed into the vacuum line, causing the pressure switch to remain open during the pre-purge phase.