Q. We have been having terrible problems with our central air conditioning unit. Our house is about 8 years old and we have a zone system (separate heating and cooling thermostats for upstairs and downstairs). For the past 2 years the unit is not cooling the house properly (heating works fine). We had the dampers replaced 2 years ago and I know the dampers are fine. We have had several repair technicians look at the unit. They always recharge the unit with more Freon (3 times in 1 summer) after claiming to fix a leak. This past weekend again a repair person claimed that we had an internal leak in the unit. He said that he had plugged the leak and then he charged the unit with Freon. Not only did this not work (our house continued to get hotter from 73F to 85F while AC was running all day) the pipe coming from the unit outside our house was all frozen over with ice (all the way to where the insulation started). Any suggestions or help will be appreciated. Thank you.

A. A system only needs to be charged once, when it is installed. If it gets a leak, the leak must be repaired, and verified that it is repaired with a vacuum test. It is a laborious process, and some homeowners would rather just juice up the machine each year than spend the funds to get it repaired. Some units have leaks that can never be identified. There are lots of fittings, small bends in the coils, and hundreds of feet of tubing that need to be traced with an accurate tool. Many Tech's don't have access to this tool, and rely on soap bubbles to identify leaks. Contact the manufacturer of your unit, and have them recommend a competent company in your area. If it is the company that you've been using, explain that they have not fixed the unit. For very hard to find leaks, there is a product available that can be added to the refrigerant similar to "Stop Leak" for your auto radiator. This product is rather spendy, about the same price as five pounds of refrigerant, but if you are charging your unit each season, it would be worth the investment. Contact the company that "repaired" the leak last time, and ask how the technician verified that the leak was repaired, and how he verified that the charge was correct.

Q. I want to install an air conditioner in my "computer" room where there is alot of heat generated to due several computers and large LCDs running all day. I have installed typical room air conditioners before but the problem I'm having is that the only window in the room shuts sideways instead of shutting down, it is also a fairly tall window, about 8 feet tall. Will a typical home air conditioning company be able to solve this for me? I image they'd have to install something in the window to cover the extra space from top to bottom since the window closes sideways, probably would look ugly too. Any advice? For the record I do have home air conditioning but the computer room is on average 10-20 degrees hotter than the rest of the house. So if I want to set the computer room to 70-75 degrees, I actually have to set the house air conditioner to 60-65 degrees which makes the living areas too cold and is a waste of energy.

A. We had the same problem..... My husband put the server into the closet, with it's own separate air conditioning duct. We had outlets put in there too, so we can put a portable fan in there, if it still gets too hot....... And in his office, we have a big ceiling fan, in addition to the air conditioner

Q. Air conditioning costs more but what exactly is the difference between the two systems? Is air recirculation effective at cooling or heating the vehicle interior on hot or cold days?

A. Air Recirculation and/or the Max A/C button do the same thing. They close off the vents that let fresh air into the car from the base of the windshield. Air Recirculation should be combined with A/C usage, which is why on some cars (older domestic US cars in particular) it's labled Max A/C. Air Recirc setting helps the air conditioner system by recirculating already cooler air through the system, rather then trying to take warmer outside air and cool it down. You can use it with heat, but on some cars (older Japanese and German cars in the US) they aren't set-up to run the A/C compressor in defrost mode. Any moisture at all will cause your windows to fog, ALL OF THEM, unless you also turn on the A/C button too. A/C doesn't really cost much more then 1 mpg on most cars. For me personally, I'll use A/C whenever I can. My comfort is worth more then 1 mpg.

Q. I think my AC unit is shot. I suspect the repair to be major, so cost is pretty important to me. Can anyone recommend a dependable repairman or repair service that won't gouge me? Thanks!!

A. Independent HVAC steve baser 214-724-1862

Q. Does anyone know a good website that teach me step by step how to service ( and do commonly needed replacement) my single room (Window /wall mounted) Air Conditioner. Googled website almost all only show companys that do air cond repair. I want this as new hobby ! T H A N K S !!

A. Try starting here: http://www.hometips.com/cs-protected/guides/centairfix.html Google diy air conditioner repair. gl

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. My car is getting older and I've noticed the air coming from the air conditioning ducts and air vents smells musty, dusty, and dirty. Is there a way I can clean the ducts and vents? Also, is this something I can get done at an auto detailer?

A. The answer to your 2nd question first. Maybe?! Some detailers will only clean/restore what they can reach, although there are some who might go the extra mile. The problem is, they don't want to be responsible for destroying your dash vents to get at the ducts. When I worked in a body shop, we simply used compressed air through the vents to blow out the dust and dirt accumulated while the car sat inside being worked on.......some people even put pieces of air freshner directly in the vents to sweeten the smell afterwards.

Q. My doctor told me I need to get my air duct cleaned, but I keep hearing all kinds of horror stories about air duct cleaners. Does anyone knows of a good air duct cleaner near San Francisco?

A. Here are some Union companies that do duct cleaning. They all do good work. Atlas Heating and AC Oakland, CA 510-893-1343 Advanced Solutions Heating and Air Conditioning San Mateo, CA 650-347-4828 Bell Products Napa, CA 707-255-1811