The fan switch “auto”–furnace doesn’t start

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Old 10-14-05, 06:13 AM
stepicz
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Angry The fan switch “auto”–furnace doesn’t start

I replaced the old thermostat with a new programme NOMA 5+1+1 this summer. The furnace is old . The AC worked fine but I have not tried the furnace until now. The thermostat has a "heat/off/cool" switch and fan switch "on/auto". If the fan switch is “on”, the furnace works with the fan. However, if the fan switch is “auto”, the fan works but the furnace does not start regardless of the set temperature.
What could it be? Did I mess up with the wires?
 
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Old 10-14-05, 09:00 AM
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?? Sounds like something is wired wrong...

How can the fan work in Auto, but not in On In what mode? Heat or cool?

This a gas or oil furnace?
 
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Old 10-14-05, 09:14 AM
stepicz
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Gas furnace

The fan works in both modes, but if the fan is in “auto” mode, the furnace does not kick in. However, if I change the fan to the “manual on” mode, the fan and furnace work together. It is gas furnace.
 
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Old 10-16-05, 08:54 PM
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Ok, is the burners kicking on, if you have the fan in "AUTO"? if the burners turns on, sounds like you don't have yoru heating speed on the fan motor.. (If the fanisn't running, is the duct hot?)

now when you turn it to "ON" the fan is using another speed... Now that you have air movent, the high limit is letting the burners run.
 
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Old 10-16-05, 09:20 PM
stepicz
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No, the burners are not kicking on if the fan is “Auto”. Once the fan is changed to manual “ON”, both the burners and fan kick in. When the temperature is reached, the burners are off but the fan is running because it is in manual “ON” position. The Auto position does nothing, although on the thermometer it is sending a signal, heat is flushing, to the furnace.
 
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Old 10-17-05, 04:39 PM
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Originally Posted by stepicz
No, the burners are not kicking on if the fan is “Auto”. Once the fan is changed to manual “ON”, both the burners and fan kick in. When the temperature is reached, the burners are off but the fan is running because it is in manual “ON” position. The Auto position does nothing, although on the thermometer it is sending a signal, heat is flushing, to the furnace.
Disconnect the "Fan" wire at the furnace and cyle the furnace. If it fires, you might have a defective T-Stat?
Phil
 
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