Power vent motor won't shut off

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Mad Plumber, Nov 23, 2007.

  1. Mad Plumber

    Mad Plumber Mad Skills

    Aug 13, 2005
    I have a natural gas water heater with a standing pilot light. My problem is that the power vent motor will not shut off. What would keep the motor running? It has an electrical switch that mounts on the top of the exhaust metal bonnet in front of the vent system with wires that lead back to the main control area. It looks like the wires connect to the thermostat area? The water heater works fine and turns on when it calls for hot water but as stated the power vent motor will not shut off. I can disconnect the switch on the top metal bonnet but other than hearing a clicking noise in the control area the power vent does not shut off. The manual that came with the unit is not much help as a sticker on the water heater said that if the indicator light is on then you have a problem and the book reads that the light should be on for the manual switch???? I can turn off the vent by either using the manual switch or unplugging the vent motor. Of course if either occurs then the heater does not turn on, so that portion seems to be working fine. The top bonnet switch has a small button between the two electrical connections and I assume is a reset but it does not seem to do anything. I checked the switch for continuity and it is "on" and doing anything with this button does not seem to make any difference. It is my assumption that this switch or sensor should tell once the unit has cooled down to shut off the vent motor but I am not sure and the book does not give any indication that is what the switch is for. All the information in the book centers around not getting hot water and nothing is said about the power vent running continuously. Any information on what should tell the vent motor to shut off would be greatly appreciated.
    D Paugel

  2. Buckeyetech

    Buckeyetech New Member

    Jul 31, 2007
    Get your meter out again, and follow the wiring schematic. You'll find where the problem is.
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  4. CHH

    CHH New Member

    May 25, 2007
    Denver, CO
    First off, I am not a professional plumber, pipefitter, or electrician. Now that is out of the way, the blower will be controlled by a relay. That relay happens to be stuck in the closed position. Locate and then pull the relay to verify that it controls the blower. You may be able to use a meter to test that the relay is stuck closed. R&R the relay.

    For some reason designers are still using icecube relays when solid states have been around for a long time. Icecubes fail and the solid states just keep plugging along.

    Yup, I'm guessing. Let me know how good of a guess it is.
  5. construct30

    construct30 New Member

    Jun 16, 2007
    NorthWest PA
    There are a lot of safety switches and relays on the power vents. Some make sure the pump is running before the flame is on and some make sure it stays on after the flame is off a while. Some work with a vacumn hose like a car. Could be a plugged vacumn hose. Some times they get soft and collapse.
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