Q. I replaced a fully functional home thermostat with a new digital thermostat from Honeywell. Now neither my heating nor my air conditioning works. I have 5 wires white (W), red (R), green (G), blue (C) and yellow (Y). When I cross a wire with red nothing powers up, so its not the thermostat: for example, crossing red with white should turn on the heating. My breaker box shows all the breakers are enabled. I see no breakers or switches on or near the heating or air conditioning units. I've also reset all the GFCI outlets. What could I be missing? I hate to have to call an HVAC expert out here to kick a breaker or something silly. This has to be something simple. HELP!! More... The furnace is in the attic; Its difficult to work with. I prefer to test with the air conditioning that is just outside the door. Tests for just the furnace don't seem to explain why the air conditioning does not work either. Much more... The house was built in 2004. Much much more... I found the furnace documentation nailed to a 2x4 in the attic; actually its more of a crawl space: a real pain and dangerous to get to and move around. Yes, I was incorrect, all wiring for the air conditioner (AC) appears to go through the furnace, so I can not just test the AC. I now believe that I was working with a live wire (R); I tuned off breakers marked "AC", but there is no breaker or breakers marked "Furnace". Based on the documentation, its likely I blew out the fuse on the furnace circuit board, a 3 amp, 32 vac fuse. I will go buy a new fuse today and climb up into the attic tonight to change it out. Thanks for the hints on the fuse; I'll look around for another breaker box too. Conclusion.... I picked up a fuse at the local auto part store; Home Depot didn't carry the type specified by manufacturer. Once I figured out how to open the second part of the door, there was the purple fuse. I pulled it and saw that it was burned out. I replaced it, went down to the new thermostat and started-up the furnace. A whole lot of drama for a 50-cent fuse. Thanks everyone!

A. Open up your furnace and see what wires go where. The R and W on the board are for heat, but they don't always set it up colour coded like that. Check for an auto style fuse on the board, usually a 3 or 5 amp (purple or yellow). You may have blown that if you put the C (common 24 volt) wire in the wrong place or crossed it with something else. Add on: If your fuse in the furnace is blown, it won't relay the signal to the AC. Nothing will work. You have to check it. If you didn't power down the furnace while replacing the stat, chances are you crossed the 24 volt with something and popped it. The thermostat does not need 24 v to work if it has batteries in it, and a furnace from 2004 will more than likely NOT burn out the transformer. The transformer will pretty much out last any other component in a furnace.

Q. The filter is completely frozen over with ice we cant even remove it.

A. Shut the AC off and let it defrost. Thats usually caused because the filter clogged from not being changed or cleaned. When the filter clogs, air can't circulate and the coils freeze up.

Q. Thinking about having one installed. Thoughts on cost to install, operating costs vs using the air conditioning? What about leaks around the installation site...hear that from a lot of people that have had them. Thanks for the help!

A. If you need an attic fan and have a vent at one end of a peaked roof, you can have a fan installed there. I did something else too. One fan in the attic blows air down into the house. Another at the other end of the house blows air into the attic. On a cool day, but with a warm attic because of sun load, I circulate air from the attic through the house. Thermostats in the attic and in the house circulate air only when the house is 70 degrees or less AND the attic is at 75 degrees or more. Also I can switch off the one that blows air into the house. On hot days, after sundown, I can blow air out of the house, sucking it in from the cooler air outside.

Q. Well my air conditioning broke and we had some people fix it and then it broke again... every time i want it to go to a certain temperature like 75 or 74 it wont move it will stay at like 88 and the 80's and i dont have the number to my ac guy and how could i fix it... i have a digital ac thermometer thing. no the outdoor fan is not runnining

A. Don't take this personally, but if you use phrases like "digital ac thermometer thing" then you aren't qualified to repair an air conditioner. You can check simple things like the circuit breaker. But if it is tripped, it is usually for a reason. And if it trips multiple times, there definitely is a problem. If you aren't satisfied with the last co. Try another one. There are lots of companies in the yellow pages. Or ask a friend or neighbor if they know someone they can recommend.

Q. What is it, and they claim that it can cut air conditioning costs by upto 50% where can i find such contractors

A. There are some cold roofing that is available to make sure the roofing is not only NOT leaking but also it reflects a lot of heat back( if you are in a tropical climate) or act as insulator if you are arctic climate. there are many types roofings that you can do . you can google them, or check the site, you can at least get some basic information on what to expect.

Q. It is 90 degrees in our house and only gets hotter they said they won't come until tomorrow afternoon. I work from home, I have a very ill dog, and these are not suitable living conditions.

A. Generally not. Obtain a court order first, you can not just decide to withhold rent. The dog will not be a legitimate reason in court, a signed lease and your AC being out for more then a couple of weeks will though. That is if the AC is covered in the lease. The next day is certainly not a problem for any reasonable person.

Q. Just looking for ideas to check for when a service technician comes out to look at my air conditioning. I know these guys are very busy this time of year and just want to be careful that I am not being taken for a ride as they tell me a whole lot of this that may not even be the problem so they could just charge more. Basically, my problem is if you feel the skinny high pressure line from my condenser unit outside it is colder than the insulated line and I don't think that is the way it should be. My neighbors high pressure line is hot, why is mine not? The cooling inside is doing okay but it feels as if it should be cooler. Also any advise on what else I could check for myself before I call the service tech would be greatly appreciated.

A. Its hard to say what your system is doing unless we had system pressures, superheat and subcooling readings. Does the air off the top of the condensor feel warm? it should be at least warm. Now your liquid line( skinny line) shouldnt be hot but it shouldnt be cold either, the heat is pulled from the refrigerant at the condensor and is cooled down back to a liquid state from a gas state, the temperature of the liquid will drop as it makes its way back to the indoor coil. You can check your temps in the house, you should have about an 18-22 degree split between the air returning to your unit and the supply air coming from the air registers.

Q. I went to school for hvac got out and started at a company but they started me out as an installer and im not sure if thats the start i wanted to this career i mean if i need it ill do it but what else can i do apartment maintanence or look for a helper position or should i just stay and try to become a lead install and how long would it take to become a service tech from an install?

A. School can teach you the fundamentals, but you NEED hands on experience to learn the things they don't teach you, the tricks of the trade if you will. Besides, isn't installing an AC part of being a tech? There are very few occupations where you can just take what you learned in school and jump into the real world. Most occupations have some form of apprenticeship. Did they teach you how to deal with customers that overlook your shoulder? Code violations you find? Dealing with building inspectors? Getting paid? Dealing with suppliers? Writing up estimates? Did they teach you EVERY cause of every problem in an AC? Have you been taught on every make and model there is, old and new? (I had to read and interpret the wiring diagram on my air handler to the ac tech working on my system that couldn't figure it out). If you're as independent as you think you are, the company will soon recognize your talents, and let you go on to other responsibilities. And just remember, with the economy the way it is, there are plenty of unemployed craftsmen that would be willing to start at the bottom again. Be humbled.