What action is needed w/System Lockout?


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Old 10-14-07, 08:35 PM
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Question What action is needed w/System Lockout?

Furnace isn't providing heat first time turning it on this season. LED diagnostic indicator sequence is identifying an external to board failure; red light 1 flash: system lockout. What does this mean & what action do I need to take? Am not finding info. in documentation. Comfortmaker Super High Effeciency Gas Fired Furnace with Total Furnace Control, Model 50A50 - 133; @15 years old, no prior issues. Might it be thermostat or limit switch related? Blower, intake, exhaust appear operational.
 
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Old 10-15-07, 07:25 AM
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I"ll see what I can find.. But look on back of the blower door, there may be some info on there for you.
 
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Old 10-15-07, 01:02 PM
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Originally Posted by SandhillCrane
Furnace isn't providing heat first time turning it on this season. LED diagnostic indicator sequence is identifying an external to board failure; red light 1 flash: system lockout. What does this mean & what action do I need to take? Am not finding info. in documentation. Comfortmaker Super High Effeciency Gas Fired Furnace with Total Furnace Control, Model 50A50 - 133; @15 years old, no prior issues. Might it be thermostat or limit switch related? Blower, intake, exhaust appear operational.
It's a little confusing:

One flash is related to a test sequence for the indoor fan motor [IOW- the fan that circulates air thru the house AND NOT the combustion air fan motor]. Are you sure you're not seeing 2 or 3 flashes? There related to a test sequence for the heat cycle. What happens when you reet the power then set the thermostat fan switch to auto and the system switch to off? Does the indoor fan start? When you say that blower, intake and exhaust appear operational exactly what does that mean? Do you mean the indoor fan and the combustion air fan run on a call for heat? If yes, does the ignitor glow? If no, check the pressure switch. Maybe it's stuck closed? There are two common failures on these units. First is a cracked heat exchanger which prevents a vacuum from being drawn thru the furnace. Second, on the fan wheel side of the combustion fan there is a restrictor ring on the fan intake. Over time, the little pins that hold it in place dissolve. Take the combustion fan apart and check it. Let us know what you find.
 
 

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