Heat came on


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Old 06-09-11, 04:41 PM
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Heat came on

From York County,PA near Baltimore

I turned on my central AC today, (not for the first time this year) and my oil furnace came on. I tried a new tstat to no avail. Even with the tstat disconnected completely, when I hit the main switch to the unit the furnace comes on. Is there some relay sticking?
 
  #2  
Old 06-09-11, 10:23 PM
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Is there some relay sticking?
Probably. Try this: Open the blower compartment door and find the terminal strip where the thermostat wires connect. Disconnect the white wire and tape the end. Put the blower door back in place and turn on the main switch. If the oil burner still fires up then you have a sticking relay and more likely than not you will need a new control board. If the burner does NOT fire then the problem is most likely the thermostat wiring.

NOTE! You posted in the furnace section so I am assuming that you have a forced hot AIR furnace and NOT a hot WATER BOILER. If you DO have a boiler then the above test will not work.
 
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Old 06-11-11, 05:53 PM
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I took your advice and tested your theory. It was correct!!! The small relay that actually sends the power to the Furnace ignition box was stuck. When I pryed open the plastic tabs and looked inside at the selonoid, it was very damp and rusty. I guess that was caused by the extreme heat/humidity we've had here it PA. Also I've had some slight icing and water condensation going on, so I guess it's time for a Recharge on the system. Thanks for pointing me in the right direction!!!
 
 

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