I have a York furnace and ac unit. The blower won't come on. :mad: The blower motor works I found that no power was going to the blower so I by passed it to stay on all the time. :cool:

What I need to know know is what is causing it there is a Honeywell circuit board (ST9120b 1005) :confused: and Honeywell controller (S8600H) :confused: . The furnace unit with blower in it is York (P-HDD12N069019A).

Can anyone help me with this. :D It doesn't work on cool the ac unit is running but the blower is off. If I just turn the blower on at thermo it doesn't work either.

Bill

Likely there is a problem on the circuit board. Chances are, the relay that controls the blower is bad. Could be in the logic too. Could even be a bad connection at the thermostat or furnace. I will post in a general description so you can figure out what to look for. Finding and fixing problems on a board are tough. You may have no other choice than to cough up big for a new circuit board.

Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors. It may be wired to have the A/C control wires return to the furnace and its controls and then a second wire goes to the A/C unit. Internal wiring may replace the green wire if the thermostat does not give you the option of fan only or continuous fan. Digital or programmable thermostats may need the blue wire connected to them.