What does the blue wire attach to in a central air unit?

Answer by  kipcat (1964)

if you disconnected the small thermostat wire the likely spot is the 'Y' terminal. There is no yellow wire in standard 4-wire thermostat wire, so contractors substitute the blue wire instead.

Answer by  frank26 (7)

The blue wire hooks into to the common terminal on the thermostat if its disconnected from the ac it hooks up to anyone of the two wires in the unit.

Answer by  BillyBingham (65)

It depends on what type of unit you have. To find the answer to this question would be to contact the dealer that you purchased your unit from.