Our new puppy pulled the thermostat wires loose from the outside air conditioning unit. No damage to any wires, but I need to know which wire goes to which. From the inside, the wires are blue and yellow. The outside unit has brown and blue. Which to which?

Really does not matter which goes to which. Will still work no matter how theseget connected. Would be good thou if you can trace which is the return for the contactor coil. At the furnace someplace is a small transformer. One wire from this transformer goes directly to the coil of the magentic contactor for the compressor. This is probably the blue wire.

The other wire is the actual power, and will go through the thermostat, and then out to the outdoor unit, and may go through other switches in the unit before going to the coil.

Again, no harm will happen if the wires are not matched up.

OK, so we have tried hooking them up both ways. Currently they are blue to blue and yellow to brown. When I turn the thermostat on, I can hear it click inside but the unit outside is still not turning on. IS it possible that pulling wires loose would have made something short? This is a new unit, only installed in our new house in September.

Not sure where these wires got taken apart. If close to the outside unit, then the wires must have been pulled off other splices or terminal strips inside the outdoor unit, or even perhaps shorted inside.

You need to check further from where the wires got broken.

Get back with more questions and details, or let us know what you found.

Ended up that it blew a fuse. We have it taken care of now!