www.hvactechgroup.com - forums

York furnace with fan set to constant run at thermostat - blower motor stalls briefly (.5 sec or so) when unit calls for heat or cool. Is this likely due to the logic in the control board, or possibly something else that can be fixed?

It's so annoying, I'm considering an off-delay timer relay to the blower, but am wondering if I'm missing a simple fix somewhere.

What model do you have?  Sometimes the control board is designed to stop the fan motor at the start of the heating cycle, until ignition, and then it resumes running.

It's a GY8S100B 12UH11C

It just stalls for like half a second. Very weird.

The continuous fan probably runs at a lower speed than heating or cooling.  There would be dip switches on the control board for the continuous fan.  If you set it to the same speed as the heating, you should not hear the fan stop.

Try turning the continuous fan dip switch #2 ON and it should run at the same speed as high stage heating.

You can also use the same speed for heating and cooling, but would need to jump the terminals together, on the control board.

Let me know which position the 2 continuous fan dip switches are set to.  We may have to set them to low stage heating speed for them to match the heating cycle.

Wow, thanks for sending that! I really appreciate your insight. Unfortunately, I think I have a different board without fan speed dip switches. I've included a picture showing that. Would my next step be removing the blue wire from "heat" and jumping "cool" to "heat" terminal?

Your continuous fan is probably using the black high speed fan wire.  An easy test would be to just pull it off the board then turn the power back on and if the fan is not running (thermostat fan still set to ON) then we know that was the continuous fan speed.

I wouldn't mess with the cooling speed so you could cut the blue heating fan wire 6" from the board.  Then cut the black fan speed wire 6" from the board and connect the 2 black ends and the blue end with a wire nut.  Then cap the unused end of the blue wire still connected to the motor with a wire nut.  You will need to strip all 4 ends of course before installing the wire nuts. 

This would mean the continuous fan, heating and cooling all use the high speed fan, and that should prevent the fan speed change you're hearing.

Again, I really appreciate you taking the time with this...

I cut the black and spliced in the blue wire from the board, then put a wire nut on the end of the blue wire going to the motor. It still does the same thing, the moment the thermostat calls for heat, the blower motor stalls.

Is this a stupid programming logic thing?

Did you verify which speed the continuous fan is using?  Is it running on the high speed black wire?

You could be right.  A lot of furnaces will stop the continuous fan, while it ignites, then it will resume.

What could be happening is the board knows it's energizing the cooling terminal for continuous fan, then on a call for heat it stops and switches to the heating terminal.  So even though we are using the same fan speed for both heating and cooling, the board does not know this, and simply de-energizes the cooling terminal and then energizes the heating terminal.

Yes, continuous fan is connected to the black wire...According to the manual, the Continuous blower is powered through the cooling tap which is black wire.

Thanks for your help with this...you should have a "Buy me a coffee" link!