Garage Furnace Troubleshoot

Discussion in 'Garages, Workshops & Tools' started by reaboy, Nov 19, 2016.

  1. reaboy

    reaboy New Member

    26
    0
    Feb 7, 2008
    IA
    I have a Beacon Morris 75K btu power vent garage furnace. I went to start it up this morning for the first time this season, and it did not ignite.

    The code flashed 3x for pressure valve fault. I got this same fault last year, and messed around with furnace checking various things, and it started working fine and did so all winter. Still do not know what caused it to start working.

    I checked the pressure valve and hose from the draft inducer. I pressurized toward the draft inducer to blow out any possible blockages. I checked the pressure valve with ohmeter while sucking and blowing on the tube and it works as expected.

    When attempting to start it at this point, the blinking code has now changed to 4 - indicating high limit, roll out, or airflow issue in draft inducer.

    - The draft inducer squirrel cage fan is running
    - The high limit switch was removed and checked with a flame and ohmeter and it checks out fine
    - The roll out switch was checked with ohmeter and it is fine
    - Just to check those circuits in operation, I jumpered both the high limit and roll out, and I still get 4 blinks.

    I have not disassembled the ducting yet, since it is a PITA.

    Any other thoughts or ideas?

    Todd
     
  2. stoney2677

    stoney2677 Veteran Member

    169
    1
    Oct 6, 2007
    metuchen, nj
    Did you cut power or just jump out? Without cutting power most likely it will show the same fault. I suggest resetting and watch it as it tries to run. There's a few things it could be. Make sure the exhaust pipe is free of obstruction.
     
  3. tom3

    tom3 Veteran Member

    10,377
    11
    Aug 1, 1999
    ohio
    Our furnace did a similar thing a couple years ago. Took apart the condensate trap that handles the water drainage from the inducer and vent pipe, cleaned it out, put some water in it to make the seal. Been fine since (knock on wood). Also, several years ago had a wasp nest built up in the vent pipe (combustion air) and it caused a shutdown and code a couple times before I figured it out. I put a screen over the vent outlet after that.
     
  4. 70lt1z28

    70lt1z28 Veteran Member Gold Member

    382
    20
    Oct 3, 1999
    Beavercreek, Ohio, USA
    Just a wild guess, but it may be a control board grpund issue. There may be a bit of corrosion on the chassis found such that it isn't getting a good, 0 ohm reference ground and it is driving the control nuts. It may throw false faults until it gets a good reference ground. Not an HVAC guy but an industrial controls guy so take it for what it's worth.
     
  5. indyzmike

    indyzmike Veteran Member

    531
    1
    Mar 21, 2002
    Milwaukee, Wi
    When you jumper the HL and RO switches, do so where they connect to the board instead of a jumper over each individual switch. This eliminates the switches and the wiring connections. Be sure to turn power off and keep one hand on the metal case of the heater while touching any terminals or wires connected to the circuit board. Any static electric discharge from you to the circuit board can immediately destroy components on the board.
     
  6. reaboy

    reaboy New Member

    26
    0
    Feb 7, 2008
    IA
    Ended up checking out every sensor and all were fine. Also check air ducting and all fine. Came to conclusion that the board in the gas valve block must be bad. Didn't bother with it any further and removed it. Purchased another Beacon Morris 75K at Menards for $500 and installed it this weekend with just a bit of adjusting due to the box being different dimensions, and locations of gas line, wiring etc. Working like a charm.

    Thanks for the suggestions, however. I had an entire day+ invested in diagnosing, and finally decided to fish instead of cutting bait.

    Todd
     

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