Furnace Circuit Board Wiring Issues (simple)?

The wires you are refering to are for the indoor blower motor. HI is for the high speed winding used for the cooling cycle and LO is for the low speed winding used for the heat cycle. Most indoor blower motors are multispeed motors, meaning they have more than one speed available so they can be used in a variety of applications. The indoor blower should deliver approximately 400 cubic feet of air per minute for each 12,000 btu's of capacity during the cooling cycle and 200 feet per minute during the heating cycle. The other wires are generally taped and are not attached. Some circuit boards provide terminals called parking terminals for the unused wires to be terminated on but not all will have these. The wiring diagram on your unit usually identifies which color wires are for which speeds. There is also a diagram on the indoor blower motor identifying which wires are for which speeds. They are typically identified as HI, MED HI, MED LO and LO. You will need to be very careful when landing the wires on your new circuit board. Make sure power is turned off to the unit before you begin the changeover.The circuit board will have different voltages in different areas. There will be both 115 volts and 24 volts working on the board. It is vitally important that you do not get the wrong voltages applied to the various terminals. It would be very helpful if you can make a drawing on paper so you can remember where the various wires are attached. Good luck.

Furnace Circuit Board

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Furnace Circuit Board Wiring Issues (simple)?

I had a repair man over today that charged me $313 to replace a small transformer and tell me that my circuit boad in my furnace was bad. (It shorted when my father tried to hook up a humidifier directly to the board..oops) Anyway, the service man told me I needed a new circuit board and that it...

Thanks for the novel on HVAC Chiefman

Yeah the HVAC guy raped you. And he wasa trying to really rape you again.

A furnace transformer costs about $14 and takes about 5 minutes to replace.

Those are for the fan blower speeds. Look on the fam motor itself and it should tell you what color is for hi and what is for low. It might also be designated on the wiring diagram with a small letter R or B for red and black.