Help with a big thermostat problem

[aaronfude]

Hi,

I was trying to move a Bryant thermonstat to a different part of the wall and everything went well except when I reconnected the wires and closed the thermostat the thermostat did not turn on. It is the first thermostat found here:

I had not turned of the A/C unit off when I was doing this and I saw a couple sparks when the wires touched. I was wondering whether I may have popped a breaker, but all breakers seem to be intact. All lights everywhere in the house are on. There's a wetness tester next to the A/ C unit and the green "on" light is not on - I don't know whether it was on before.'

I would appreciate any suggestions. Are there tests that I can perform to identify what's not working?

Many thanks in advance,

Aaron

[ds549]

if you have a circuit board in your ac/furnace. it may have blew a circuit. it will look like a burn place on the cuircuit board.

[Big_Jake]

I'm thinking the same, but more accurately, it is a 3A fuse. Your furnace might have even come with a spare. Otherwise you might be able to get one at an auto parts store or maybe Radio Shack. Don't put in a bigger one!

JK

[unclemon]

Aaron, most standard thermostats in the US work off of the 24 volt ac transformer located inside the air handler. That's the part where the blower is. If it's a split system with the furnace/air handler, evaporator coil and ductwork inside the house, the low voltage transformer will be in the furnace. A vented cover on the furnace will usually slip up and off with little trouble. On the inside you will see where the 120 volt ac supply and the thermostat wire usually with a brown plastic jacket about 1/4 inch in diameter enters the unit. If your furnace/air handler was installed properly there will be what looks like a light switch on or near the unit to turn the power off for servicing. You may have blown a low voltage fuse located in a holder or on a control board. Some units have a small circuit breaker. If you're unlucky, you may have blown the 24 volt transformer. There is usually a wiring diagram glued to the inside of the furnace or blower access panel. The standard and simplest wiring for most HVAC unit thermostats is as follows:

R red 24 volt ac hot G green blower/fan W white heat Y yellow AC B blue 24 volt ac ground

The blue wire is not normally connected when a non-electronic thermostat is in use. Here is a link that may be of use to you:

I can fix most HVAC units with my eyes closed except for the part where I touch a hot wire and get the hell knocked out of me. Safety first, kill the power before you change out any parts. I hope this post helps you.

[8~{} Uncle Monster

[Meat Plow]

Make sure you got the wiring correct. Google it if you need to.

[mm]

House breakers are much much bigger than the amount of current used internally to control things. For that there are glass fuses, or maybe some other kind of small fuse.

When this happened when I was working on my friend's, there was a spare fuse taped close to where the original fuse went. You dind't give the brand of your AC, only the thermostat. It's the AC that determines the fuse size, and when you find where the fuse goes, somewhere near there it will say what size fuse to use. Perhaps on a diagram, or on the circuit board, certainly someplace in the AC and certainly also in the owners manual that came with the AC. IN my friend's case, he had half of the AC ownners manual in his files, and there was a second half stuffed in the condensor cabinet outside, that the installer never took out and gave him. (Is that typical? They leave it there for the repairmen?) I think both halves said what size fuse to use, and one or both halves had a drawing that indicated where the fuse went.

In that case, I blew the fuse by letting the control wires to the condensor outside touch each other, but if you got sparks at the thermostat, they are probably smart enough to make it blow a fuse, probably the same fuse.

Next time, turn it off before moving wires, OK? And turn it off before you replace the fuse, too. If not, you won't kill yourself, (I don't think. :) ) but you might blow the second one.

[mm]

And of course, on the blown fuse itself, it will say what size it is. There are several letters and numbers but it will say 3A if it is 3 amps.