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  1. #1
    Seasoned Camper Devinh2's Avatar
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    Furnace not working-help

    Hey Gang, woke up this morning (0430) to a humming/vibrating sound by the propane tank (street side), and a 45 degree trailer. Went out and switched tanks on regulator and sound went away. Tried to start the furnace. The blower comes on for 10-15 seconds, and then shuts off. Stove works, fridge works, hot water tank works!! Voltage is good, and I ran the generator just to make sure (boondocking here). Not hearing a spark on the furnace at all. Any ideas besides sail switch or mother board??
    And does the outside panel just pull off after taking screws out?? Seems to be hung up on the exhaust tubes and I don’t want to force it unless that’s the only way. THANK YOU!!

    Signed- Why is it so damn cold in Arizona!!
    Devin & Roberta & Bizee (Border Collie)
    2015 Ram Laramie Cummins w/Aisin 4.10 CC LB 4x4
    Titan 55 Gal midship fuel tank
    2018 384GK Solitude
    B & W Companion Hitch
    4 - 165 watt solar panels, 2800 watt Magnum inverter
    Blue Sky 30/24il controller, 4 FullRiver 6V 250AH Batts

  2. #2
    Site Sponsor gbkims's Avatar
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    Furnace Operation - Just copied some info from an older thread on furnace operation, don't know if it matches your furnace.
    - https://www.mygrandrv.com/fo...l=1#post135227

    "How far does your system get in this chart?

    Time Line
    Description - Sequence of Events

    Start Thermostat Calls for Heat
    The wall thermostat controls the operation of the furnace by reacting to room temperature, this allows current to flow through the On/Off switch to the module board.
    The module board constantly checks for a minimum 9.5 volts. If there is not 9.5 volts,the module board will go into a stand by mode until adequate power is supplied. It will then resume normal operation.
    Upon a call from the thermostat, the module board thermostat circuit will go active.
    The sail switch circuit is verified as being open. The blower output is energized. Blower motor starts.

    15 Seconds Purge Cycle
    The module board will then verify that the sail switch circuit is closed and motor is up to speed.
    If this circuit remains open for 30 seconds after the blower motor starts, the module board will go into lock out and shut down the blower motor.
    The module board checks that the gas valve relay contacts (which are located on the module board) are open before the ignition sequence starts.\
    The board has a pre-purge timing circuit of (approximately 15 seconds). This allows the chamber to purge.

    7 Seconds Ignition Cycle and Flame Sense
    The module board will energize the gas valve and enable the high voltage spark output to the electrode for 7 seconds of ignition time.
    The module board will then check for flame sense to verify successful lighting of the main burner flame.
    Sparking will then be terminated and the gas valve and blower outputs will remain energized. If ignition is successful the module board will monitor the flame sense, sail switch and limit switch circuits, and the thermostat inputs during the heating period.
    The flame is sensed through the spark wire and electrode. Therefore, it is essential that the electrode is properly positioned in the burner flame

    Try Ignition Board
    If the flame is not sensed after seven (7) seconds, a second 15 second purge cycle will begin followed by a second Trial-For-Ignition sequence.
    After three (3) Trial-For-Ignition attempts with no ignition of the main burner, the module board will de-energize the gas valve immediately and blower will run for 3 minutes and then shutdown in lockout.

    Heating Cycle
    If during the heating cycle, the limit switch circuit opens and remains open for 5 minutes, the module board will go into lock out and shut down the blower motor.
    If this occurs, the thermostat will need to be reset for the furnace to operate.

    90 Second Shut Down
    When the thermostat has reached its set point and the demand for heat ends, the gas valve will be de-energized and the flame will go out. The post purge period of 90 seconds begins. When it times out, the blower motor output is removed, and the blower stops."

    Troubleshooting Guides & Tips > Furnace Troubleshooting > https://manuals.heartlandowners.org/
    Last edited by gbkims; 01-03-2019 at 08:58 AM.
    - Gene

    Kim & Gene
    2015 Reflection 317RST
    2017 Ram 3500 CC LB 4x2 6.7 CTD AISIN 3.73 DRW Auto Level Rear Air, BD3, Prodigy P3, Aux Tank

  3. #3
    Rolling Along carnolddsm's Avatar
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    The outside panel pulls off. Sometimes the tubes in the intake and exhaust stick. Be firm but gentle when pulling.

    Given the short run time after the blower come on it is pointing to the sail switch. Though it could be the DSI board.
    Colan and Marilyn Arnold
    Des Moines, IA - kind of, on the road full time.
    Currently in Durango, Colorado
    Momentum 350M originally, now a 397TH

  4. #4
    Seasoned Camper Devinh2's Avatar
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    Thanks to Colan, we are back up and running!!
    Devin & Roberta & Bizee (Border Collie)
    2015 Ram Laramie Cummins w/Aisin 4.10 CC LB 4x4
    Titan 55 Gal midship fuel tank
    2018 384GK Solitude
    B & W Companion Hitch
    4 - 165 watt solar panels, 2800 watt Magnum inverter
    Blue Sky 30/24il controller, 4 FullRiver 6V 250AH Batts

  5. #5
    Rolling Along carnolddsm's Avatar
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    Quote Originally Posted by Devinh2 View Post
    Thanks to Colan, we are back up and running!!
    Glad to have been of assistance.

    For anyone reading this thread, the problem was a loose connection at the limit switch. If there isn’t 12volts on the hot side of the sail switch with the blower running, check the limit switch before changing the DSI board.

    BTW - this is the second furnace I’ve seen in the last couple of months with a flaky limit switch connector.
    Colan and Marilyn Arnold
    Des Moines, IA - kind of, on the road full time.
    Currently in Durango, Colorado
    Momentum 350M originally, now a 397TH

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