I have a Lennox G12Q3-120-6 model furnace. Does anyone know if there's a way to manually run just the blower without heat?

There are no switches on the outside that I can see (other than the power cut-off), and the only 2 panels are only to be removed when servicing.

FYI - I want to be able to use my furnace blower to circulate air from my basement to my upstairs.

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    Does your thermostat not have a fan control? – Steven Jul 27 '12 at 0:35
  • All it has is a lever to change the target temperature. Is that something that is generally included on a thermostat? I've never seen one that has a built in fan control. – Quasipickle Jul 27 '12 at 3:55
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    Yes on most of them you can set the fan to either auto or on which keeps the fan running all the time.. – Steven Jul 27 '12 at 12:04
  • I'll have to look into that. I imagine an HVAC repairman would know? – Quasipickle Jul 27 '12 at 14:18
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    Yes a HVAC tech will definitely know, but installing a thermostat is really easy so I would definitely suggest it as a DIY project! – Steven Jul 27 '12 at 14:31

With a old school thermostat that you just adjust the temp with normally there are not any additional wires to run the fan. It can be done but will require more wires and an additional switch or new thermostat. A few houses back I had a gas forced air system like yours I added a fan over ride switch at the furnace , this turned on the blower and was helpful at cooling the house off in the summer.


Your furnace probably has a G terminal on its board. You can connect that to a thermostat's G terminal (requiring at least three wires to the thermostat), or you can jumper to the R terminal with a manual switch mounted to the furnace housing (or anywhere, really--you could run it to a standard wall switch).

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