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STEP
Check connections and retry. If current is near typical value
(4.0 to 6.0 microamps) and main burners will not stay on
longer than a few seconds, check the following:
- Air leakage around igniter bracket.
- Inadequate flame carryover on rough ignition.
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- Low manifold pressure. Reference installation instructions
- Slow opening gas valve. Gas should flow at full pressure
within 4 seconds after the gas valve is energized.
If the above items are OK replace the variable speed fur-
Clean flame sensor with fine sandpaper and make sure it is
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properly positioned then recheck current. Current is typically
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Will main burners ignite and stay on?
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- Make sure perforated disks are in combustion-air
- Pressure tubing going to gas valve air pressure fitting for
- Remove gas valve air pressure fitting and check gas valve
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- Ensure vent and combustion-air pipes are not reversed.
- Add restriction to combustion-air pipe or lengthen a few
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While the unit is operating in low heat jumper R and W2.
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Do you have burner pulsation's in high heat?
Turn off the power and disconnect the jumper across the R
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Turn power on and jumper R, W/W1, and W2 thermostat
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Do the main burners stay on longer than a few seconds?
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Furnace will operate at low-heat but will not ignite on low-
- Low manifold pressure. Reference installation instructions
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for proper low-heat manifold pressure.
- Slow opening gas valve. Gas should flow at full pressure
within 4 seconds after the gas valve is energized.
- Air leakage around igniter bracket.
Furnace will not operate or ignite on low-heat. Check the
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Reference installation instructions for proper low-heat mani-
fold pressure. Turn low-heat regulator adjustment clockwise
1/4 turn. Repeat until furnace will operate in low-heat. Then
set to the proper manifold pressure. Re-orifice if necessary.
ACTION
- Low inlet gas pressure.
for proper manifold pressure.
nace control.
4.0 to 6.0 microamps.
Is current near typical value?
Replace electrode.
Do you have burner pulsation's?
Check the following:
vent inlet.
kinks.
for blockage.
- Burner orifice size and alignment.
- Inadequate flame carryover.
feet if possible.
and W/W1 thermostat terminals.
terminals.
Do the main burners ignite?
Do you have burner pulsation's?
Disconnect jumper from R and W2.
Do the main burners remain ON?
heat. Check the following:
- Inadequate flame carryover.
- Flame sensor location.
following:
- Flame sensor location.
- Very low manifold pressure.
YES
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44
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NO
GO TO
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183
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8
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