Two yellow wires on old thermostat?

Question

i have a conventional a/c and gas furnace. i am installing a digital thermostat to replace the old one. one yellow wire is bunched with the others and has a bare end and i believe that is the cooling wire. the other is coming from behind the sheetrock and has a crimped loop. both are attached to the Y on the old thermostat. what would that second wire be for? i don't think i have 2 cycles for my cooling, how would i know? please help.

thanks

first time home owner

Answer 1

Is it possible that whoever installed the a/c and heat ran the wire from the outside a/c unit to the stat instead of making the connection in the furnace. That would be the only reason I could think of for having 2 wires to the Y terminal.

Answer 2

One wire runs from the stat to the AC to turn on the AC. The other runs from the stat to the furnace to tell the furnace to turn on the fan.