We had Heat and AC unit installed in July. Worked great until mid September. We'd left for one week and when back the AC fan would come on but the unit outside was not on. Thought maybe a fuse and replaced but still not working. Called the installing company and they came out and said it needed a new circuit panel. Asked why - don't know was response. When he brought the circuit panel (if he did) he said it still wasn't working due to a cut wire. Cut wire where? Don't know was response.

The technician ultimately ran a wire from the unit outside, up the side of the house, through the attic vent and to the part of the unit that's up there. (Totally exposed to anything that might want to cut or eat the wire?)

I asked what this wire is - said a T-stat wire. I asked why it worked without that wire for 2.5 months and now we need that wire. Don't know was response, the technician will have to tell you.

Well, the technician will be out tomorrow because when I tried to use the heater this week I discovered that NOTHING is working, no fan, nothing - to heat or A/C.

I'm having concerns with this company (suppose to be extremely reputable and was a referral). Is something not right with this picture or am I just being paranoid? Why did he put that wire there? Why did he not know where a wire was cut to begin with?

Anything I should ask for or know before he comes to the house tomorrow?

Thanks for your help - Linda

Aruuuuuuuuuuuuuug. You may need all the help I can give you. Well a good tech might be even better. This is how things work:

Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors. It may be wired to have the A/C control wires return to the furnace and its controls and then a second wire goes to the A/C unit. Internal wiring may replace the green wire if the thermostat does not give you the option of fan only or continuous fan. Digital or programmable thermostats may need the blue wire connected to them.

I came across the niftiest gadget for trouble shooting, a voltage detector. There are several brands. I have a GB Instruments GVD-505A, less than $15 at Home Depot. Touch it to a hot wire, and the end glows red. Find the doodad that lights it on one side, and not the other, and you have the culprit.

Cut wires are where cut wires are. I had control trouble with my old furnace and A/C several times. Eventually when I tore it out to put in a new one, I found an inaccessible place where the chipmunks had eaten the insulation off the thermostat wires. As above, you must have a small pair of wires going from the furnace to the outside A/C unit. Usually they are run out of sight if possible. If something happens to one in some hidden area, running a new one down the side of the house might be a temporary solution. Since this is a new installation, I hope you won't have to pay most of the expense. If you drove a nail in the wall the wrong place or something, likely you will have to pay for that.

Here is my new A/C unit with the armored wiring and insulation. http://www.photolocker.net/images/Labman/KatetheAC.jpg

One more point. Do you have a little pipe coming out of the attic that drips water when the A/C runs? Track it down and keep an eye on it. That is the moisture the A/C takes out of the air. If it quits dripping water when the A/C runs, that means the little drain is plugged up and soon water will be running down on your ceiling. You might ask about a float switch and an alarm.

Thank you for your suggestions. I must have some really hungry "chipmunks" because everything worked fine since installation, I turned it off to go to Alaska for a week (I highly recommend Alaskan cruise to anyone considering it) and upon return - not working anymore.
So, when this tech refers to this T-stat wire he ran outside the house, that doesn't mean it has anything to do with the thermostat in the hallway correct?

I have a warranty so I haven't had to pay for anything - yet.

Cute dog, want to trade for two English Mastiffs?

For the outside unit to run, both terminals of the transformer must each connect with a terminal on a relay outside. Usual practice is for one side to go the thermostat and back, and then join the other and the 2 run outside.

Can't have Kate. She is now working as a dog guide half way around the world. Mastiffs? Note the rigid conduit for the power feed to the compressor.