AC and Furnace turn on at the same time

Installed the C-wire (and thermostat) last night. Attached is the before picture from the furnace. It seems to be working overall except for the fact that the ac and the furnace start running at the same time. Living in Minnesota this is not ok right now!

As you can see there are 2 wires going to “Y” I attached both those wires into the “Y” area of the C- wire adapter. Was that correct? Is that why the AC keeps turning on? (This wasn’t a problem with my old thermostat)


Your issue is due to connecting both Y wires to the adapter, only the wire going to the thermostat should be connected to the C adapter. The way you have it wired will cause both to come on