12 year old Nordyne gas pack blower fan runs, but Ignitor won't light

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  #1  
Old 02-06-16, 05:38 AM
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12 year old Nordyne gas pack blower fan runs, but Ignitor won't light

I installed a new heat exchanger (the old was rusted and cracked), making sure to take lots of pictures first. After reattaching everything I turned on the gas and power, then watched the ignitor fail to light the gas 4 times. I turned everything back off, waited a couple of minutes, then turned it all back on. It lit and appeared to run great (the flame did have the occasional yellow flicker, but this thing hasn't run in two years). When it got warm in the house, we turned the temp down on the thermostat. An hour later we turned it back up and nothing. The Ignitor will not light, though the red status light is on and steady. The blower fan runs constantly when the unit has power even with the thermostat fan setting to auto; this was a problem prior to replacing the exchanger because the roll out switch had tripped. The roll out switch has not tripped since I replaced the exchanger. Any ideas on how I can diagnose and fix this problem?
 
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Old 02-06-16, 02:19 PM
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Unfortunately, tearing a furnace apart to replace the heat exchanger could result in reconnecting something improperly. And it could be pretty much anything.

<<, then watched the ignitor fail to light the gas 4 times. >>


So I presume that the hot surface ignitor got white hot, the main burner gas turned on for 2-4 seconds, then the main burner gas shut off and the ignition cycle began again.

Is that right?

The HSI may not be getting hot enough to light the gas. Usually it should get white hot.

I'd measure the AC voltage being applied to the ignitor, which should usually be 120 VAC. A poor electrical connection in the circuit board might cause a lower voltage to be applied, resulting in the HSI not getting hot enough to light the gas.

If that were the case, usually the HSI would be getting red hot rather than white hot.

If the voltage is normal as described above, be sure you have the HSI located properly to light the main burner gas.

If all that is fine, I'd replace the HSI.
 
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Old 02-06-16, 05:34 PM
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high limit or break in 24v safety switch such as roll out or even more commonly loose wire because you were just in there and possibly dis lodged a wire.
 
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