How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Phil Your Own Question
Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 5648
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
23932409
Type Your HVAC Question Here...
Phil is online now
A new question is answered every 9 seconds

I need a C wire new thermostat. My furnace has a /C

Customer Question

I need a C wire for my new thermostat. My furnace has a B/C terminal which currently has the Y wire attached to it, even though there is also a Y terminal on the furnace. There is a black wire and grey wire that are unused, but neither of them seem to have power when connected to the B/C terminal. Any ideas?
Submitted: 1 year ago.
Category: HVAC
Expert:  gotoman for ac replied 1 year ago.
If you will look you may have one of the yellow wires from outside unit attached. Just attach one of the wires not used black or grey and attach at furnace to b/c and C on thermostat. Russ
Customer: replied 1 year ago.
I don't have a yellow wire. I'll include some pictures. You can see the two unused wires, but the thermostat still doesn't power on when I use either of them and plug them into the B/C terminal on the furnace and the C input on the thermostat.
Expert:  gotoman for ac replied 1 year ago.
Check furnace board for fuse. It may be blown. Do you have a red light on furnace board. Remember door switch has to be pushed in for power to furnace. Russ
Customer: replied 1 year ago.
Good point. I checked the board and don't see any red lights. However, if the fuse were blown, wouldn't that mean the current wire in the B/C slot would not work?