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. I have an outside central air conditioning unit, it is approx. 80 degrees outside and extremely humid, also very hot inside the house with fans running. The air is set to 70*, yet the air coming out of the vents feels to be room temperature and is NOT cooling the house down. Approx. two months ago, the landlord had a technician come out, and he said we had a slow freon leak, and although he filled it with freon, I was told he did not fix the leak. What is causing the air conditioner to do this? I cannot go in 100* weather without air conditioning. Any help would be appreciated :) and thanks in advance!

A. It almost sounds like the tech overcharged the unit. Either way he is supposed to fix the leak. He was not supposed to add refrigerant to a system known to be leaking. Make sure the fan is working on the outside unit. If it is not the system has no way to remove the heat from your house. Ask your landlord to call a different tech out to look at it. This guy was a fool.

Q. Please excuse my ignorance, but is there a portable air conditioning unit (blows out COOL AIR in a HOT ROOM) without being attached/fixed to the wall, as in carry it with you just plug it in to a wall socket and have it blow out cool air. I know this may seem like a dumb question, but a simple answer would be much appreciated. Thank you!

A. There are two units that are kind of like that, but not quite. one is called a swamp cooler. they evaporate water to absorb thermal energy in a room, but make the room more humid, and only really work in dry climates. however, they are relatively cheap to buy and use little energy. the other is a regular AC unit, but, this is not a window unit. they make one that is a free standing floor unit that can be pushed around and plugged in anywhere. however, the only downside is that there is a 3 or 4 Inch diameter hose that comes out of the back of the unit that must be run outside, through a window or a cat door or something. the unit is similar to window units in that it must move the heat from the room to the outside, but it does not have to hang out the window. they are about as expensive as regular window units. and are much more portable. you just have to point the hose outside. just remember, the heat has to go somewhere. it is very hard to just make it disappear (like an endothermic reaction, a reaction that takes heat)

Q. If you know someone that has and operates their own company, not a big company where you have to wait on hold when you call them i'm adding some rooms in my house and need some bids for the a/c thanks

A. Honest Air i dont have the number but you can find it online good luck

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. Water sometimes backs up and my unit turns off. I have to shoot water into the PVC pipe outside and suck it out to get it going again. Are you supposed to put bleach or something else in the PVC pipe?

A. I used to have this problem but when I got a new unit install they put a clean out opening in the condensate pipe up in the attic. I just poor a little bleach down the pipe a couple of times each season. No more problems.

Q. I just moved into a new home that had never had the ducts cleaned. The house is a ranch with gas forced air heat on one zone with about 9 vents. I found this company on a coupon for $45 which included unlimited vents and a couple access holes. When the company began their work they found mold and the price skyrocketed from $45 to $1400. Does this sound like a screw job or is that price accurate for mold removal and duct cleaning?

A. Mold removal/remediation is entirely different from air duct cleaning. However, it is not uncommon to find mold in your air ducts. That is why we recommend the Electro Breeze Duct Mount UV kit at http://www.allergy-relief-air-purifier.com/air-conditioning-filters.html. This unit will eliminate mold and bacteria from your indoor air and keep your air conditioning coils clean from mold. You must consider that to remove the mold from your air ducts, the air duct cleaning company is entering into a potentially dangerous situation for their employees. This requires expensive equipment and a person with the skills to do the remediation properly. Now that they have knocked the mold loose, you will need the high efficiency filtration and ultra-violet light of the Electro Breeze DMUV kit to kill and capture the mold spores in your indoor air. I hope this helps.

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.