I designed my house and was active in reviewing the contractors recommendations based on the Manual J analysis. When all is said and done the old adage of 12,000 btu (a ton) for every 500 sq ft of floor space is pretty accurate, except I would modify that for any known major variable that you know would cause a problem. In my case, I had shade trees all around so there's less direct sunlight load, but I have 9' ceilings which is more air to condition. My split system has a 13 SEER that was sort of cutting edge for 1996, a single speed scroll compressor. The blower is a variable speed one, which is key to my system because I have a humidistat installed (inexpensive). During the heat of the S. Texas day it will run at higher speed for maximum cooling due to the heat load, but since it runs for like 12 minutes, humidity is totally wrung out. In the pre-dawn hours when the humidity is like 85%, but temp is 72, it doesn't run much cause there's no heat load. When it does run, the humidistat tells it its getting humid in here so it runs at slow speed so it wrings out the air, slowly getting to the selected temp setting. I have the humidistat set for like 63%, so if it achieves 64% or higher it automatically shifts to high speed. I like it alot. Last week it was 97 outdoors, the AC ran like 12 minutes then was off 18 minutes. Before you select your SEER, you should understand that number directly relates to your energy bill. Ex: Since a 16 is 33% more efficent than a 12 (diff of 4 divided by 12), an electric bill that would be $100 with a 12, will now be $67 with a 16 (of course a 16 costs more to buy, but rebates/tax credits help). Good luck.

Moving the wire connectors while unit was on pretty much eleminates broken wire in one of them. Don't rule out the contactor yet. It's possiable for it to occasionaly fail to completly close. While the condenser is failing to run although t-stat is calling for cool,check accross the two low volt connections on contactor. If you find 24v but contactor isn't engaged(closed) ,that says bad contactor coil or if contactor is closed maybe the contact points are dirty or partly obstructed from making contact. Have you tried manualy closing the contactor. I can't add much encouragment regarding the circut board other than mention that many Carrier boards have an led on it that flashs a self diognostics code.

With thermostat technology available now it is very easy to have full control of what type of heat you are using and when. The stats use an outdoor temp sensor and can be set to run the heat pump in one set of temperatures and the alternate source at other temps and also run one or the other or both depending on the temperature so you can get the best bang for your heating buck. If its above 35 degrees my heat strips are totally locked out unless there is an unlikely defrost needed. If it is below 35 the stat will run the heat pump and stage in strips as needed down to I believe 10 degrees the heat pump is deactivated and it only operates on the heat strips until the temperature comes back up outside. This allows seamless control with no need to get up and make any adjustments other than picking the temperature you want inside the home. The stat can still be manually set to emergency heat or auto mode just like the old systems. If gas prices shoot up you can set the pump to run on down to whatever temp you want say 10 degrees or not even shut off at all. If gas prices drop you can have the heat pump locked out totally or at say 40 degrees. It sounds like it might be worthwhile to check into or start considering upgrading the whole system but until then a fan motor and or capacitor isn't a massive undertaking or expense. BTW at temps above 30 degrees a heat pumps efficiency really ramps up.

I'm guessing a 2BR condo shouldn't need 3 tons of cooling. Moreover, an oversized system won't dehumidify as well as a correctly sized unit and will most likely be noisy. What is the sq ft of the condo? How far from the beach is it? Get a detailed heat gain/loss analysis done to confirm the system size needed. Are you replacing both the outdoor condenser and the indoor air handler? I'm not familiar with any of the 3 units you were quoted (?!) You might want to get quotes from a Trane, Carrier, or Rheem dealer.