The Trane XV90 furnace is a two-stage condensing furnace fueled by natural or propane gas that is available in upflow or horizontal positioning. The furnace has a variable speed inducer and a variable speed blower and is designed for residential use. If a problem arises with the furnace, an error code flashes on the control panel lights. One potential error is a furnace lockout, which is not something that every furnace user knows about.
Vent Pressure Error
Three flashes on the Trane furnace control board means that the vent pressure is too high or too low, which then activates the pressure switch and causes a lockout. Check all incoming and outgoing vents on the furnace air system, including on the furnace, and clear away anything that may be blocking the air flow. Then reset the furnace.
High Temperature Limit Lockout
Another switch on the Trane furnace that will trip and lock out the system if not quickly resolved is the high limit switch. This switch is designed to protect the furnace if the furnace temperature exceeds the high limit temperature point, which can damage the furnace or even create a health or safety hazard. The system will shut down as a result. If the error light on the Trane is flashing four times, lower the thermostat to just above air temperature, and press the red "Reset" button. If the problem occurs again, disconnect power, and contact a qualified service professional for help.
If the error light on the Trane is flashing regularly, the ignition may be the problem. Open the gas valve fully in a counterclockwise motion to make sure the gas supply is turned on. Increase the temperature on the thermostat, and turn the mode to "Heat" after making sure the vents are all clear of blockages. Disconnect the power to reset the furnace, and contact Trane if necessary.
If the Trane furnace error lights are flashing twice and then pausing, or the furnace will not restart after pressing the "Reset" button, a system lockout has occurred. This means that the furnace has either automatically reset itself a few times but could not resolve the issue or that the user has pressed the "Reset" button on the control panel excessively. If the light is flashing twice, you need to contact Trane or another qualified technician for assistance.