Gas furnace not firing


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Old 02-21-13, 10:55 AM
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Gas furnace not firing

From last night, my furnace (Amana Air command 80) stopped firing when the thermostat calls for heat, the fan kept on blowing air. The LED on control module (White Rodgers 50E47-843, which replaced with original one 2 yrs ago) is always OFF. In the manual, there is two different clues:
1. OFF: Internal Failure.
2. After calling for heat, yellow LED should light for 2 seconds, if no, check Low Voltage to module (TH-TR). If no voltage:Check Limit Switches, check vent pressure switch (if used).

Should I check limit/pressure switch, or replace control module?

Thanks!
Eric
 
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Old 02-21-13, 12:25 PM
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Take the cover off the burner compaertment of the furnace.

Carefully observe the sequence of events that occurs when you turn up the thermostat to call for heat.

Deascribe that sequence here in order and in detail.
 
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Old 02-21-13, 08:24 PM
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SeattlePioneer,

Thanks for promptly response. I removed the cover of furnace and checked it again. It seems control module died. After turning up the thermostat, fan starts to blow, but LED was not light up with Yellow or any other color. I also measured TH-TR, it's around 26.8V, seems ok with limit/pressure switch, right? What else should I check?
For control module, is there any fuse to replace? Or to get the new module, should I get exactly same one, or any alternative which is more reliable (at least last longer than 2 yrs)?

Regards,
Eric
 
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Old 02-22-13, 04:09 PM
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You would need to post the make and model of the ignition module to get a reply to the questions you pose.
 
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Old 02-25-13, 07:10 PM
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The ignition control module is White Rodgers 50E47-843.
 
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Old 02-25-13, 09:23 PM
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Which fan blows? The main blower or the inducer (venter)?

Does the main blower ever come on?

At the ignition module, check L1 120v hot and L2 for voltage. Should be around 120v AC.

If there's 120v between L1/L2 and 24v ac between TH/TR, after 30 seconds terminals HSI and HS2 should get energized. (check for line voltage)

If HSI/HS2 get energized yet the igniter doesn't heat up, the igniter is most likely bad.

If HSI/HS2 never get energized when the module has line voltage (l1/l2) and control voltage (th/TR), the module is probably bad.

Troubleshoot at your own risk.
 
 

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