Furnace Problem (Electrical or Overheating??)


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Old 06-25-16, 08:00 AM
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Furnace Problem (Electrical or Overheating??)

About a month ago we noticed no A/C. Went downstairs and the furnace had no power. The little red light was off. Opened it up and checked all the connections and the breaker and couldn't find anything. Let it sit overnight and tried it again in the morning and the red light came back on for about 3 seconds and the furnace started but then suddenly it lost power again. Tried it a few times and then suddenly everything started up fine and it ran without issue for a month.

Then yesterday the same thing happened. No power, red light off. Opened it up and let it sit overnight and in the morning the red light came back on for a few seconds and then quit. After a few tries it is running fine again?

Any ideas?
 
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Old 06-25-16, 10:42 AM
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Please tell us the brand and model number of your furnace and A/C so we have something to go on.
 
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Old 06-25-16, 01:33 PM
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It is a Trane Xr90 and is 10 years old
 
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Old 06-25-16, 10:03 PM
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Opened it up and let it sit overnight and in the morning the red light came back on for a few seconds and then quit
Opened what up ?

It almost sounds like a defective blower door switch.
 
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Old 06-25-16, 11:04 PM
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Sorry, when I said "open up", I mean take the service door off. At this point I press the pressure switch manually to activate the furnace.

Update: Now the furnace only starts for a few seconds and then loses power completely (red light off), and will not respond for about an hour. After an hour I can press the pressure switch and the furnace will begin to start but then lose power and go dead again for about another hour.
 
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Old 06-26-16, 09:24 AM
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Problem solved. I used a load (lamp) to trace power and there was a loose connection in the external switch (between breaker panel and furnace). Vibrations from the furnace running were enough to break the connection which caused the weird loss of power after startup.
 
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Old 06-26-16, 11:24 AM
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Good catch! Thanks for the update.
 
 

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