What's this wire for?

[Marc M]

Wuts up with the wire? Haven't seen this one before.

[Jim Luttrall]

Low voltage sensor that kills the unit if water is present.

[Marc M]

Big Jim...thanks.

[Jerry Peck]

Low voltage sensor that kills the unit if water is present.

Then proceeds to cause the unit to leak condensation all over the place as a result of that shutting down. :)

It is a result of pressure from the HVAC contractors to allow that switch without also requiring what would stop that from happening.