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Old 11-08-2011, 11:31 AM   #1
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limit switch problem on heater


my lennox heater is showing the limit switch as being open. the blower works but there is no flame and the gas is turned on.how can i fix this?

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Last edited by the3cfam; 11-08-2011 at 11:40 AM.
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Old 11-08-2011, 01:27 PM   #2
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limit switch problem on heater


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Originally Posted by the3cfam
my lennox heater is showing the limit switch as being open. the blower works but there is no flame and the gas is turned on.how can i fix this?
Replace the limit.Change the filter and check that the evap. coil is clean

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Old 11-08-2011, 07:47 PM   #3
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limit switch problem on heater


A bit more time for a better answer... Limits trip because a furnace overheats. They can only open and close so many times before they are ruined. Overheating is caused by incorrect gas pressure or not enough air flow. Dirty filters or dirty coils are the most common causes but a failing motor or weak capacitor can also give low air flow. That should get you going in the right direction.
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Old 11-08-2011, 09:11 PM   #4
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limit switch problem on heater


Undersized ductwork and people closing registers in unused rooms and restricting the airflow also is a problem. Only proper way to know is to get the gas pressure checked and temp rise thru the unit tested by a Pro.
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Old 11-08-2011, 10:04 PM   #5
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limit switch problem on heater


Some of those limits are resettable, some manually and some intermittenly (self resetting) if you will, but that doesn't mean that it won't trip again. The limit is simply telling you that something is wrong, of an overheating issue which needs to be addressed.
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