Carrier furnace wont light automatically

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  #1  
Old 12-27-08, 11:57 AM
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Carrier furnace wont light automatically

I have a 1988 Carrier model 58GS125-BA furnace. The automatic pilot will intermittently not light. When the thermostat reads below the heat setting, gas will flow to the pilot (you can light it with a match) but there is no spark. When the system is working properly, I hear a rapid series of loud clicks from the gas valve as the igniter begins sparking. When the system is malfunctioning, I do not hear these clicks. Do I need to replace the gas valve?
 
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Old 12-27-08, 12:10 PM
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Sounds more like the spark box.
 
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Old 12-27-08, 12:14 PM
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I presume the spark box is the black box at the other end of the red wire running from the spark electrode. Is this correct? How can I test this?
 
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Old 12-27-08, 12:25 PM
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If you have a meter you can check for 24 volts a/c current at the terminals on the black box when the pilot is emitting gas.
 
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Old 12-27-08, 12:35 PM
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I checked and I have 24 VAC across the terminals while the gas to the pilot is flowing - the unit happened to be sparking at the same time. Do I need to perform this same check when the gas is flowing but the spark is not present?
 
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Old 12-27-08, 12:47 PM
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Yes, if you have 24 volts and it is not sparking it is faulty. It should maintain 24 volts at the box until the call for heat is satisfied but will stop sparking when th pilot lights.
 
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Old 12-27-08, 01:02 PM
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OK. I checked it again after the furnace lit - gas still flowing to the pilot (and the burners) and no spark present. I still read 24 VAC across the two terminals on the black box. By the way, this box is labeled "Spark Ignitor Ignition". So it sounds like I need to replace this part, Correct?
 
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Old 12-27-08, 01:10 PM
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Yes, that part is faulty and needs to be replaced.
 
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Old 12-27-08, 01:12 PM
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Thanks for the advice. You sound like you know what you are talking about, are you in the HVAC business?
 
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Old 12-27-08, 01:22 PM
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Was in the trade for 15 years. Retired now due to an illness.
 
  #11  
Old 12-27-08, 01:24 PM
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Thanks again. You have been a big help.
 
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