Upon arrival thermostat was showing code 205, indicating that a gas valve relay was stuck closed and not allowing system to heat home. Reset system and cleared alert code, system came on with no issues and ran for 30 minutes. Cycled system on and off five more times to see if fault code will occur again. No fault code showed up and system ran without any issues present. Informed homeowner to give us a call back if code shows back up. Informed homeowner that gas valve is likely intermittently working. Homeowner will hold off on repair for now until part fails before repairing. System is operational at this time.