Replaced an old thermostat. Wires touched creating a spark. I think there is a short. Is there a DIY fix?

Question

Tried to replace an old mercury thermostat with a digital one. Wires accidentally touched (don't know which ones) and there was a spark. I continued putting everything together only to realize that the A/C won't start. I'm guessing I shorted the wires? Turned power on/off for the entire house but no luck. I'd like to fix this DIY if I can. Any suggestions that don't involve ripping up drywall?

Answer 1

When you shorted the wires you probably ruined the 24v transformer. They have an internal fuse that needs a surgeon to get at.



Go to the furnace or heat pump and look for the wire that heads into the wall. It usually has a brown jacket covering from 4 to 8 small wires. These wires go to a terminal strip. On one end of the strip you will see the red wire (also the yellow, green and white). Follow the red into the unit and it will go to a fuse or straight to a small transformer. Test the transformer with a meter for 24v AC. If no voltage is there make sure 110v or 220v is going into it. If you have supply voltage and no output then the transformer is fried.



Turn off the power to the unit. take a snapshot of where the wires go or make a diaphragm (you may have one on the inside of the cover, anyway) and replace it. They are very common and easy to find. and replace



Even if the red goes to a circuit board there should be a transformer nearby.



Happy fishing.

Answer 2

There is a fuse in the furnace wiring that will need to be replaced. Turn the power off to the furnace before working on it. Take off the cover or the door, follow the wires and find the break in the wires, remove the fuse, go to the hardware store and buy a new fuse. insert this fuse, then and only then should you turn the power back on. Some new furnace units have a control panel and for this wou will need to buy a new control unit from the manufacturer look up your model furnace on-line and then "call them" before the purchase so you buy the correct part. Your drywall should not have to be touched

Answer 3

did u try fan only theres a jumper between rc and rh make sure thats there then look in your furnace around were the blower motor wires in if your lucky youll have a 3-5 amp fuse like for a car if its there and blown replace it with same size if its not there and still no power call a tech you blew transformer gl

Answer 4

Unless you're racing it, don't worry -- even if you are racing, replacing all the wires probably would be a waste of money, but people who race their cars like everything to be brand new.. Each wire in there does it's job, and it doesn't care what the other wires look like.

Answer 5

check fuses in the furnace, use a continuity test to make sure.