OK...problem is now resolved (I think). I managed to get the cover and light fixture out of the unit, then removed the fan assembly to see if I could see things better. There is a contra-flow "flap" that was stuck in an open position. I could close by pushing it shut with a screwdriver, but then when I opened it again, it stayed open. Perhaps some lint build-up or something like that, but anyway, there was a plastic tab that is to act as a counter-balance to make the thing shut again so I attached a small paper clip type thing to it to give it just an extra bit of weight. Now when I push it open with a screwdriver, it opens and then closes back on it's own. As for the venting piece, I really can't see if it's venting directly into the soffit, but I suspect you are right. It is so far back into a corner of the house, it's virtually impossible to see. Thanks to all for your help and advice. I love this kind of teamwork.

Some of these comments are reiterated again and again. I am a retired HVAC/R professional with over 40 years experience. There is no cut and dried answer to most of these questions. Most of the answers are mostly correct in that you need to seal your ductwork, insulate it if it is in non-conditioned space (attic/crawl space), and the ductwork needs to be laid out correctly to supply AND return the correct amount of cfm to each room. After that, NO air conditioning technician in the world can correctly diagnose an air conditioner's problem unless several criteria are met. First and foremost, BOTH the condenser coil and the evaporator must be clean and the furnace (air handler) filter must be clean and not restricting flow. If you call a company out to your house and the technician comes up to your house with his gauges and refrigerant tank FIRST THING and immediately hooks the gauges up and starts putting refrigerant in, my advice is not to call that particular company back again. The coils MUST be clean before you can even begin to decide that the system is under or overcharged. Next you must make sure that you are moving the correct amount of cfm for the size air conditioner you have. 400 cfm/ton is the nominal amount for air conditioning. NOT ONE person has mentioned how important this is. On MANY occasions, I have seen brand new equipment installed and no one can figure out why it won't work! With brand new equipment, we know the coils are clean so that is not the problem. Let's say we have a house that is 2400 square feet and a new furnace and air conditioner are installed. It's a 105,000 btu furnace and a 3 ton unit. The homeowner complains that their old furnace and a/c (same size) worked fine until they had to have it replaced. Technician after technician comes out.....they hook up their gauges and add and remove refrigerant and can't figure out what the problem is. The a/c runs almost all the time and the pressures are correct but the relative humidity in the house is REALLY high and they can't figure it out. Some technicians recommend a whole house dehumidifier as a fix. C'mon people, let's not put a bandaid on this problem. What most technicians tend to forget with an installation of new equipment is that the new furnace doesn't KNOW what size air conditioner it is being mated with! The new furnace can typically be mated with (and has the blower assembly to work with) anywhere from a 3 ton to a 5 ton unit. These furnaces will have as many as 6 different speeds for the drive motor. A 5 speed motor is more typical but the factory sends these furnaces out USUALLY with the lowest speed set up for heat and the highest speed set up for cool. This means with the 3 ton unit (which needs 1200 cfm delivered), on the highest motor tap speed from the factory, the furnace is delivering 2000 cfm or more! Moving 2000 or more cfm through a 3 ton evaporator will result in a "delta T" of 10 degrees or less which explains the unit running almost continuously and the high relative humidity in the house. These technicians need to remember that they need to look in the installation manual to find the right motor tap speed to utilize with the size a/c being mated to the furnace. With the advent of the 95+ % furnaces, we are seeing ECM motors being deployed in the furnaces. These have no speed taps, but instead have a motor that is in essense a variable speed motor. The technician still needs to consult the installation manual as the motherboard in the furnace will have dip switches to set the motor drive unit to supply the desired cfm. Now, some "rules of thumb." IF your coils are clean, IF your furnace filter is not clogged up with dirt and providing a restriction, IF you are moving the correct amount of cfm for your size a/c, IF the superheat is correct and IF the subcooling is also correct, you should get a delta T of between 17-22 degrees and your supply temperature should be between 51-55 after the unit has run for 10 minutes or longer.

It sounds like your home had floor furnaces at one point. The large return air grilles sound like old openings for floor furnaces, used a long time ago. Where to start? First, your system should have filters somewhere in the return duct or inside the air handler or furnace. I would look really good to make sure you haven't missed something. I've seen filters placed in really weird places. Sometimes filters aren't found for years. By then they're pretty stopped up. As far as the return grilles being large, the larger the better! One thing that kills your system and your energy efficiency is duct work that's just too small. Modern systems are made to run with very little static pressure in the ducts, around 1/2 inch. That's not much, so I wouldn't worry about the large ducts. The filters are another story. You really need a filter in your return duct somewhere. If there's not one, i would install filtration. Usually the cheapy filters work best as they cause the smallest pressure drop in the duct. You mentioned the refrigerant leaking out. If you have a refrigerant leak it should be repaired. That stuff ain't cheap. Besides it's illegal for a technician to keep adding without repairing the leak. If someone is having to add refrigerant, you definitely have a leak, no question about it. If the service provider you called did not look at your duct work, did not tell you your system had a leak, and did not offer sound recommendations, please ditch them and find someone qualified. As far as your system coming on and off every ten minutes or so, that's called "short cycling" and isn't good for your system, your energy costs, or your comfort. It sounds almost like your system is either too large for your home or you have massive air infiltration. Either way, this needs to be addressed. Really, I would recommend you find a good service provider in your area that can be trusted to offer technically correct advice. I usually find it best to ask friends, co-workers, or other family who they use and trust. In the meantime, you may want to check out a couple of articles I've written dealing with heat loads and your comfort. Here's one HERE if you would like to read it. Let me know if there are specific things I can help with. I'll be happy to help if possible.

Probably best to know something about motors and pulleys and bearings to be able to do this. First I would check the breaker as noted above. If it's tripped, there will be a reason for that. It could be a one-time thing but chances are something is broken or on the way out. So, before turning it back on, check that the blower (probably a big squirrel cage) turns by hand. If not, the motor bearings may have seized up. If it turns but not easily, it may need lubricating. Some squirrel cages will have oil cups at either end of the shaft. If the motor bearings are the ones that are stiff, it may be time for a motor anyway, even if it will turn. It could have tripped the breaker drawing too much current and turning too slowly. Replacing a motor is moderately difficult and requires some wrenches and an ability to read and understand the motor info plate and get a suitable replacement (at an HVAC or motor supply shop). And to hook up wires safely. You'll have to decide if you are up for it.