how do I install a fan/blower switch on my furnace


Old 07-08-10, 02:18 PM
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how do I install a fan/blower switch on my furnace


I would like to add a switch to my furnace so I can turn the fan/blower on and circulate air in our house in the summer.

If you look at picture 'B' below you can see I wire sticking out from the 'R' connection - I tried to jump the 'R' connection with the 'GH' but it did not work after I put all the covers back on and flicked the power switch.

(The R to GH is something I read on another forum)

I'm hoping someone can look at the furnace setup in the pictures below and tell me how to wire this to turn the fan on all the time (with no heat).

Thanks ...

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Old 07-08-10, 05:39 PM
Join Date: Oct 2002
Location: Hamilton County, Ohio
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Does your thermostat have an auto/manual switch? If so, flip the switch and problem solved.
Old 07-23-10, 05:00 PM
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Assuming your thermostat -doesn't- have a fan switch option, the much more involved and not very recommended way would involve bringing 120v through a switch to the red lead currently at "Lo", and back out the white lead to common. Be sure the red lead is no longer attached to the board when you do this. This would simply bypass the board and power the motor directly. Remember that you'll have to reconnect it to the Lo terminal come cold weather.

Again, I don't actually recommend doing this, but there's the info you need. Exercise all due caution when working with electricity and electrical components. Also, there may be a neater way to do this, but I can't tell from the wiring diagram. At any rate, it wouldn't be more effective...just neater.
Old 07-23-10, 06:36 PM
Join Date: Dec 2004
Location: San Jose,Ca
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I wrote some stuff and then changed my mind once I realized this is not a furnace currently set up for a/c, which means no cool relay.

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