Furnace locked out


Old 02-15-04, 06:42 AM
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Furnace locked out

I have a Intertherm Furnace that decided not to turn on anymore. Its about 5 yrs old. The Control Module Status Indicator blinks 3 times and the book says its in lockout because of a failed ignition attempt, a gas valve error, or a false flame sensed during the warmup period. The false flame one is suppose to reset itself. When I go to turn on the furnace all it does is make a humming noise and after a minute or so the light starts to flash. I included some pics so hopefully someone can help me out.


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Old 02-15-04, 08:46 AM
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The pros will be here soon for expert help. Think I would turn the power of which should reset the computer. If it has the same problem after that you need the experts.
Old 02-15-04, 09:18 AM
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In you pictures, I cant see if that model furnace has a draft induction fan, if it has is the fan running?? The Sequence of events is this

1.- Thermostat calls for heat

2.- small induction fan starts

3.- Sensor (air Pressure) senses fan operation

4.- Controller gets signal the fan is running and powers on hot suface ignitor

5.- Thermal sensor opens gas valve and ignition is complete

Timer waits fixed period and starts Circulating Fan!!

If the small inductoin fan doesn't start then the whole cycle stops and the indicator blinks 3 times (test by shorting the 2 wires connected to the pressure sensor) But only momentarily until the hot surface starts to heat up!!! then shut down!! Problem isolated to induction fan

Good Luck Jerry
Old 02-15-04, 12:01 PM
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Turns out it was the igniter. It had a small crack in it. A new one was put in and its working like a charm.
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