"FAN ON" switch causes AC to be on all the time

[tipsrfine]

Problem probably lies in a spider web of low voltage wires somewhere above the basement where somebody wire nutted the outdoor unit to "G".

[tac0967]

Thanks for your help guys. The problem actually was the green and yellow wires being switched! I watched him fix it; the fan on now works like it's suppose to. I'm still trying to figure out how I never had this problem with the old furnace... Anyway, thanks again!

[RoBoTeq]

Thanks for your help guys. The problem actually was the green and yellow wires being switched! I watched him fix it; the fan on now works like it's suppose to. I'm still trying to figure out how I never had this problem with the old furnace... Anyway, thanks again!

Uh, yea....some of us would like to know how that worked as well

[Milk man]

Uh, yea....some of us would like to know how that worked as well

Are you still doubting?

Maybe the yellow wire never went to the where we assume it went to, maybe it just landed on the thing "G" usually controls. Maybe.

[Milk man]

Thanks for your help guys. The problem actually was the green and yellow wires being switched! I watched him fix it; the fan on now works like it's suppose to. I'm still trying to figure out how I never had this problem with the old furnace... Anyway, thanks again!

Thanks for the update.

[RoBoTeq]

Are you still doubting?

Maybe the yellow wire never went to the where we assume it went to, maybe it just landed on the thing "G" usually controls. Maybe.

I suppose that could have happened. But if the Y and G wires were connected properly to everything else and only switched at the stat, there would be other issues. And, I don't see how the system could work properly before if either the Y or the G controls were not wired.

[54regcab]

I suppose that could have happened. But if the Y and G wires were connected properly to everything else and only switched at the stat, there would be other issues. And, I don't see how the system could work properly before if either the Y or the G controls were not wired.

As long as the furnace gets +24v on the G and/or Y terminal the blower will run. If Y and G were backwards at the stat the system will still work as long as the condenser/furnace both had 24v.

[HVACTechNC]

For me, around here the learning never stops!

Thanks for the update. I learned something new today. Now I can call it a day.

[RoBoTeq]

As long as the furnace gets +24v on the G and/or Y terminal the blower will run. If Y and G were backwards at the stat the system will still work as long as the condenser/furnace both had 24v.

If it is a variable speed blower, yes. Most psc motor furnaces, the Y terminal is just there as a connection spot and not connected to anything in the furnace. We were not told anything about the furnace that I recall reading.

[beenthere]

If it is a variable speed blower, yes. Most psc motor furnaces, the Y terminal is just there as a connection spot and not connected to anything in the furnace. We were not told anything about the furnace that I recall reading.

Most newer PSC blower furnaces will run the blower if thy receive 24 volts on the Y, weather or not the G has 24 volts.

All the Affinity PSC blower models do.

[RoBoTeq]

Most newer PSC blower furnaces will run the blower if thy receive 24 volts on the Y, weather or not the G has 24 volts.

All the Affinity PSC blower models do.

Ahhh, good to know.

[Mr Bill]

Most newer PSC blower furnaces will run the blower if thy receive 24 volts on the Y, weather or not the G has 24 volts.

All the Affinity PSC blower models do.

That would be correct, and the G usually operates the fan on speed.

[54regcab]

On my system G runs the fan at heat speed, Y runs the fan at cool speed. G input is ignored when the furnace gets the Y command.