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The igniter element heats up but the pilot valve will not power up and flame.

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chancell
chancell Member Posts: 9
I have an older 1998 Heil gas furnace that stopped working. Has been working flawlessly. Honeywell smart valve replaced about 7 years ago.

HVAC tech diagnosed following problem.

The igniter element heats up but the pilot valve will not power up and flame.

Upon removing the ignitor and holding in his hand, it ignites and the pilot flames and if held close enough to the burners will ignite the burners. When touched to the frame, the same happens, the ignitor heats up and will not flame.

Removing ground wires does not help.

Checked all wiring and cannot see any broken insulation or broken wires. He checked wiring with ohm meter and everything checks out.

Pressure switch is fine.

Honeywell SV-9501 smart valve and ignition replaced. Still no flame. Transformer and circuit board replaced and still no solution.

HVAC tech (26 yrs exp.) dumbfounded.

Had an electrician out this morning and checked all wiring from hvac to breaker box and all checks out.

Any ideas greatly appreciated!

Comments

  • Tim McElwain
    Tim McElwain Member Posts: 4,628
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    By chance did someone reverse the polarity? What is the number on the board ST 9101, ST 9120 or ST 9141 or is it some ones board other than Honeywell?

    At the connection for the ignitor assembly on the valve do you have 24 volts when the thermostat is not calling. Then do you have it when the thermostat calls. If you have it both times and you are still having a problem it is the igniter/sensor or the pilot it is inserted into.
  • unclejohn
    unclejohn Member Posts: 1,833
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    Did you clean the pilot? Blow through the pilot tubing with hi pressure nitrogen.
  • JStar
    JStar Member Posts: 2,752
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    Sounds like voltage is shorting to ground, causing a false flame signal too early in the ignition sequence. Were any of the ignitor or gas valve wiring harnesses changed?
  • chancell
    chancell Member Posts: 9
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    Hi all,

    Thanks for the replies. Had a new HVAC tech out Wednesday who was recommended by the original tech. This tech is from a larger nearby city and a large hvac shop. He replaced the wiring harness from the smart valve to the ignitor. He removed and cleaned the tubing from the smart valve to the igniter and cleaned the orifice to the igniter (remember the igniter is new) - said he thought it was restricted. He then adjusted the gas output on the smart valve to the igniter to 10 mBars from 5 mBars. Said 1st tech had not changed default factory pressure setting. the furnace fired up and worked. He has no idea why we thought it was a short.
    However, tech said that there is a vibration in the blower motor wheel that makes a noise. I had not heard this noise before and thus have no idea how this came about. I will post this as a new thread.
    Thanks for your help.
  • chancell
    chancell Member Posts: 9
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    Should also point out that this is propane and 2nd tech said the igniter orifice is smaller and can easily clog.