[boswell]

Hi All. I am new to the board and this site. Super excited to be here.

I have been troubleshooting my York Furnace Model GY9S100C20UP11H.

About a month ago I replaced the York furnace Blower motor as it was very loud. Everything was working great and had no issues (york furance, heatpump, and propane). Then the other day I noticed that the heat pump condenser unit outside was running and then shutting off after about a minute or two and switching over to propane a lot. Temps were in the 40s and low 50s outside so this should not happen.

What I have determined is that whenever my heat pump comes on it starts to heat, but then the furnace blower motor will not come on. It then fails over to propane and the blower motor starts and heats the house.

If I place the thermostat in the fan on mode, the blower will not come on. Set it to heat and the above cycle occurs. Set it to AC and the same problem (Heat pump kicks in and runs but inside blower motor never starts). Set it to emergency heat and all works fine on propane.

Troubleshooting:

Have replaced the run capacitor

I have tested that there is varying resistance to the different fan speeds from high to low using my cheap old multi meter so it seems like the blower motr itself is fine.

No errors or flashing diagnostics code. Thermostat Green wire is supplying 24 volts to the board calling for fan.

The fan is connected to "Hi Cool" and I have verified that there is not120v current on the "Hi Cool" when the fan is set to on.

Any thoughts?

It looks increasingly like the control board is bad. Just want to check here before replacing it.

 

[Windows on Wash]

Welcome to the forums. I am sure one of the smart HVAC guys will be along soon enough.

 

[yuri]

There are 2 fan relays.

One for heat and the other for AC.

It sounds like the heat one is OK if the fan starts with the Propane and gas burner which it does? Correct?

The AC one is the one which works with the fan ON and the AC and heat pump and if the fan is not working with either then it is probably sticking open.

If you can read the wiring diagram and find which one it is and then tap it with a screwdriver and it starts then you know 4 sure that is the issue. Looks like you may need a new circuit board.

 

[surferdude2]

Also, check the voltage on the green wire or G terminal when manual fan is set. If 24 vac is there, you likely have a failed board. Measure from C to G terminal to be sure of having the correct reference.

 

[boswell]

Hi guys.

Thanks for the pointers and help. I did test the voltage G and C wires and am getting ~24v when fan is set to on, so the thermostat is calling for the fan to turn on.

"Hi Cool" is the only PIN that does not get 120v. Heat, EAC and HUM appear to all have 120v when the system is turned on. I need to find a wiring diagram or schematic as it bugs me not knowing precisely what failed.

I went ahead and ordered the new control board and will let you know how it goes. Thankfully we still have emergency heat and the temps are supposed to go back up tomorrow, so only have 1 night where it will be low 30s.

 

[surferdude2]

If it was a dire emergency, you could connect the fan to run constantly by jumping power to it. You would need to disconnect all motor leads except the neutral and run power to the high speed lead while securing the other leads safely so they can't possibly connect to anything.

 

[boswell]

Hi All,

Replaced the control board and all is fixed now. I wish I had pulled the control board off the unit first and looked at it. Clearly, a circuit was fried as indicated in the picture.

Thank you guys!

Looks like I can't add pictures.

Here is the cold link. https://www.diychatroom.com/members/boswell-569545/albums/hvac/39443-burnt-circuit/

 

[surferdude2]

Yep, you could have fixed that! Now you have a nice spare for round 2, which we hope never happens. :smile: