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Camper44's avatar
Camper44
Explorer
Mar 30, 2020

Hydro Flame 8500 series furnace

Hello all,
I have a hydro flame 8500 series furnace, the thermostat has an on-off switch,and a 3 position fan switch, low,auto and high,the furnace will not light on the auto setting but if I switch it to the low setting it will fire up, then shut down after reaching temperature. I turn the power off and fan switch to auto,then have to repeat the process to fire back up again when it chills back down again, any input would be appreciated. Thank you
  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    Mar 30, 2020
    T-stat 'fan' setting should have NOTHING to do with furnace operation
    Auto,low,high would be settings for A/C Unit fan

    Furnace fan is controlled via furnace system
    DC from a FUSED source goes to furnace...then backfeds to t-stat
    When t-stat closes (temp setting lower then room temp) the DC then energizes a 'timed delay relay' OR a Blower Circuit on circuit board (depends on year model)
    When energized FAN is powered by the DC from fused source.
    Fan runs/triggers Sail Switch which then allows DC thru sail & limit switches to circuit board for gas valve & spark electtrode for ignition.

    8500 series should have an LED light on circuit board which would indicate a Fault Code

    Could be relay Or blower circuit, could be sail switch sticking, could be loose connections


    This is wiring diagram using a 'relay'



    This is a wiring diagram using blower circuit on circuit board



    Got a voltmeter ----use it and trace the DC

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