Gas Furnace- no response on Auto

Old 10-16-05, 08:41 PM
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Gas Furnace- no response on Auto

When I put the thermostat to Heat/On position, fan to Auto, and raise the temperature to 75 degrees, room temp was 50 degrees, there was no response. The thermostat was flashing “heat” which means it was sending a signal to the furnace to kick in but the furnace would not start. However, when I changed the fan to manual “on”, both the fan and furnace started. When the temperature was reached, the furnace would stop but the fan would go on because it was on ‘on’ instead of “auto”

It is an old Lennox gas furnace. Would anybody have any idea what could be wrong?
Old 10-17-05, 05:15 AM
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Low speed on your blower could be bad or the fan limit or fan relay.

If it's been more than a few years since a clean and safety check get it done and have them check this problem.
Old 10-17-05, 07:30 AM
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Could it be something wrong with the thermostat wiring? I purchased a new programmable thermostat this summer, NOMA 5+1+1, followed the manufacture’s diagram on wiring, and the AC worked fine. This is the first time I turned the furnace on since the new thermostat was installed.
Or it is just coincidence?

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