How to make nest thermostat turn off fan when AC turns off?

[u/SDPlantz]

I set my nest thermostat cool to a certain temperature with the AC. When it hits the temperature, the AC turns off, but the fan keeps running. How can I make it so the fan shuts off as well?

Edit: here is a link to the wiring

https://imgur.com/a/hIVuBRV

[u/sryan2k1]

Turn off Airwave.

[u/SDPlantz → u/sryan2k1]

Airwave is off

[u/sryan2k1 → u/SDPlantz]

Need to see the wiring at the furnace end then.

[u/SDPlantz → u/sryan2k1]

Ok, I’ll try to find them

[u/Rubix321 → u/SDPlantz]

Find the manual for the furnace as nd see if it has its own airwave-like feature

[u/Yayman123]

I looked at the images, the wiring seems correct thermostat side. The fan should run automatically when the HVAC runs. Your thermostat generally wouldn't force it on/off unless you tell it to run the fan on a schedule or timer. The G wire is the one that controls the fan, for testing it should be ok to unplug it? (Only mess with the wires with the power off of course). If the fan works and shuts off correctly by your hvac, then it's a thermostat issue, and you can leave it unplugged but lose thermostat fan control. If not then the problem should be with your HVAC and is beyond my knowledge.

[u/SDPlantz → u/Yayman123]

So the fan does turn on when the AC turns on, but the fan keeps running after the ac turns off.

I’m testing it out right now. I think when the ac turns off, the fan turns off briefly then kicks back on a couple seconds later.

[u/Somar2230]

Sound like it's not wired correctly the fan should shut off when the target temp is reached, if you have Airwave enabled the fan will run for a short time after the AC compressor stops.

[u/SDPlantz → u/Somar2230]

Yeah, the fan will run constantly until we select “off”.

Bummer. We had someone install it, so not sure about the wiring.

I put a link to pics of the wiring

[u/AStuf]

Check your colors as it almost looks like you have a green wire in C and brown in G. The most common color for G is green.

[u/SDPlantz → u/AStuf]

There is no green wire.

Brown is in g. Blue is in c.

[u/AStuf → u/SDPlantz]

Okay, bad eyes on my side but that is a strange color scheme. I would still double check the wiring at the furnace.

Note that many furnaces have a timer on the blower that continues to run it after the request is turned off. This is done to increase efficiency.

[u/gnat_outta_hell → u/SDPlantz]

Try removing the Rh wire and put some electrical tape over the bare end, then put the tstat back and see if it tells you there's no power. These are supposed to be able to vamp off the heating power wire, so if your fan and common are reversed this diagnostic should result in a no power error on the nest and prove that C is connected to the fan control and the fan is receiving a constant 24V signal from the common - which is on G and causing the fan to run constantly.

If it still has power, then C is in fact connected to the 24V common and there may be a wiring issue in the HVAC system.

[u/titsmcgee4real]

This might be obvious, but there is a fan option in the nest... Do you have it set to ON?

[u/SDPlantz → u/titsmcgee4real]

Nope, but for some reason the fan is turning off now. Idk if I reset it by disconnecting it or something but seems to be working now

[u/that_girl_shel]

If you go into the Nest settings, is Airwave set to On?Nest settings

[u/JonJackjon]

If the fan goes on when there is a call for cooling, then the fan must have gone off at sometime. Perhaps your A/C (or your nest) keeps the fan on for some period of time after the cooling has ended.

I don't know about the Nest but other thermostats have a setup menu where some of that type of control is input.