# Fan will not shut off after installing Nest 3



## caiken76 (Jan 28, 2016)

Hello

So I know there is lots of articles out there about this, but they all include the G wire issues. In this case I do not have one.
So installed a new Nest 3 a couple of days ago.
Had to run a new 18-5 wire downstairs for it as I only had a two wire setup from my previous mercury thermostat. Before I installed the nest, the furnace would turn on, run the heat, run the fan for a bit longer, then shut off, and it would cycle quite a bit as my house is old and leaky
*After* I installed the Nest, the heat comes on once in a while, but the fan runs constantly. I should say that it has in fact turned off a few times so its not on 24/7
Here is what I cannot figure out.
I have a C wire running from the C on the furnace to the C on the Nest to power it. 
I have a R wire running from furnace to Rh on the Nest
I have W wire from furnace running to W1 on Nest
There is a bridge wire running from R on furnace to G on furnace to I would assume turn the fan on when the thermostat calls for heat.
I do not have a G wire running at all and nothing is attached to that terminal

Now, what I cannot figure out is, How is it possible that the thermostat is turning just the fan on but not the heat with no G wire.
I should mention that I blew the 3amp 24V fuse on the control plate and had to replace it, so had to turn the furnace off then back on again to reset it. 

Would this be a furnace issue in that something is set to run the fan for obscene amounts of time after the heat cycles to cycle air?

Any help is appreciated.


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## caiken76 (Jan 28, 2016)

*few pics*

Few pics


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## ben's plumbing (Oct 6, 2011)

the jumper from r to g ....that is wrong...from what i see that is why the blower is running constant...furnace... or heat pump...


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## supers05 (May 23, 2015)

Was that jumper always there? I assume that you don't have AC? If you ran the extra wire, why not disconnect that jumper and connect g to the nest? 

Fuel furnaces are supposed to run fan by themselves without G being wired. (At least ever model that I've seen) Wiring G in that situation would only be for your comfort and not necessary. 

Cheers!


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## caiken76 (Jan 28, 2016)

supers05 said:


> Was that jumper always there? I assume that you don't have AC? If you ran the extra wire, why not disconnect that jumper and connect g to the nest?
> 
> Fuel furnaces are supposed to run fan by themselves without G being wired. (At least ever model that I've seen) Wiring G in that situation would only be for your comfort and not necessary.
> 
> Cheers!




yes good call, the Red is a 24V line so its triggering the G terminal at all times no matter what. Forgot that it is R and not Y that is live. 
No the jumper was there already. It is a pretty new furnace (just bought the house and was here when I bought it). I would assume the air guy put it in.
Will try removing it and see what happens! or just connect it to the Y terminal so when the furnace calls for heat, the G will get a signal.


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## caiken76 (Jan 28, 2016)

worked like a charm. Not sure why I didn't figure that one out on my own. May have been the 8 hours I spent fishing wire through the wall and a blown fuse. 
Cheers


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## beenthere (Oct 11, 2008)

Why not just connect the G terminals of the Nest and furnace, now that you have the wire for it.


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