Blower Runs Continuously - Troubleshooting Tips

I have a State water heater with a power vent, and for some reason, the blower is running continuously. Is that a normal condition, and if it is not, how to fix the problem? 

Most of the time, the problem with the blower is related to the air pressure switch or vent system.

  • First, check the wiring of the air pressure switch that is properly connected and is not damaged.
  • If the wiring is OK, ensure that the sensing tube that leads to the air pressure switch is not kinked or damaged and is correctly attached.
  • If the water heater is equipped with the Intelli-Vent control, you might have to replace it if it does not energize the blower. 
  • Use the multimeter and when the blower is running, check the resistance in ohms on the air pressure switch contacts – the contacts should close and show continuity.
  • A further test should be taken to see if the element is defective or not. The test involves measuring the air pressure at the sensing port on the blower. If the pressure is below the activation point of the switch, you should check for the restrictions in the vent, too many bends, debris, and dirt…. But if it is above the activation point, then the air pressure switch has to be replaced.
  • The air pressure switch might open if the temperature limit switch is open (defective). The switch opens its contacts when the temperature of flue gases rises, and if the contacts are open at room temperature, the switch has to be replaced.
  • Next is to check the vent system installed per codes and manufacturer instructions, has the correct vent pipe size, and the length and number of bends don't exceed the maximum allowed.
  • Check for the blockage in the vent pipes and remove anything that prevents normal airflow and transfer of the exhaust gases.