Background: I have an older Trane furnace (manufactured 8/1994) made by American Furnace Inc. (The Trane Company, Trenton, NJ) model TUJ080A936A0. The module controller is by White-Rodgers Emerson Electric Co. Model 50A52-101. There is no gas pilot light.

Problem: Recently, my gas valve will turn itself off prior to the desired temp. Based on the controller, it will attempt to restart (I see the ignitor turns on) for 2 attempts, however, after it turns itself off, any reattempt is to no avail. Even with the ignitor on (bright orange color), the gas valve will not open (i.e. no gas).

Temporary solution: I have to turn the thermostat OFF, then turn it on again. Since the temperature setting is still above current room temperature, the furnace will turn on as normal. Unfortunately, after several minutes it will turn itself off again. This process will repeat continuously, i.e. I have to turn the thermostat OFF and ON again to get it going. Also note that if I did it too soon after the gas valve turns itself off, by cycling the thermostat will not make the gas furnace working.

Need help: Please help me to understand what could be the problem