Ducane CMPB050U3A fails to light LED Fault Code 3

Discussion in 'HVAC Heating & Cooling' started by bigd_1, Nov 7, 2010.

  1. bigd_1

    bigd_1 New Member

    Nov 7, 2010
    Unit has SV9520H Smart Valve which flashes 3 times after a call for heat..
    The Inducer Blower doesn't come on at all.
  2. bigd_1

    bigd_1 New Member

    Nov 7, 2010
    Following Honeywells guide http://customer.honeywell.com/techlit/pdf/69-0000s/69-1383.pdf this occurs after the inducer is energized which never happens so I am confused where to look next. The Pressure Switch isn't that expensive but I don't think it is bad and I replaced the inducer already because last year the motor made some noises when starting that made me think it was on the way out so I jumped the gun on replacing it already..

    3 Flashes

    Pressure switch circuit was still sensed as
    open 30 seconds after the inducer was
    energized. System is in 5-minute delay
    mode, with inducer off. After 5-minute delay,
    new ignition sequence is initiated.
    NOTE: SmartValve On/Off switch in OFF
    position during a call for heat generates this
    flash code.

    1. Move SmartValve control switch to ON> Valve is on
    2. Inducer and inducer wiring. Already replace
    3. Low line voltage power supply.
    4. Airflow proving switch operation, tubing, wiring.
    5. Obstructions or restrictions in appliance air intake or
    exhaust flue system that prevent proper combustion air
    6. Other devices (such as auxiliary limits) in the airflow
    proving switch circuit.
    Last edited: Nov 7, 2010
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  4. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    Do you know for sure that the inducer is never energized, or is it that the inducer motor is bad? That is the whole point of the pressure switch....to prove that the blower is running.

    Since this is not a new system, and used to work, we can assume that the line voltage polarity is correct, but it it worth checking. For sure it is worth checking that the grounds are still good. This system is sensitive to polarity and good ground.

    Failures in complex system are often by visual or simple tests of "the basics"
  5. bigd_1

    bigd_1 New Member

    Nov 7, 2010
    yes i know for sure and this is a new inducer
    i am thinking it is the fan timer
  6. marcar

    marcar New Member

    Jan 6, 2011
    Sumner , IL
    could be your fan timer could also be the sv9520h valve.
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