"The last time it acted up i checked and had the 24 volts coming from the thermostat to the board but no voltage from the board to the contactor which is what made me think a pressure switch may be locking the voltage out" I want to be clear about something... When you say "the board", do you mean the control board that sits inside your furnace\blower? If so, that's what I mean as well. That board does a lot of things (including the timed shut-off delay mentioned below) but as far as I know, all it does to turn the condenser unit on or off is sent 24 volts over two lines to the unit, specifically the contactor within the unit. There certainly may be more complicated control systems out there but that's the way traditional A\C systems were set up. In such systems, the control board has absolutely no idea of what any "pressure switch" inside the condenser unit is doing, no idea of whether you have no coolant in the lines, no idea of any sort of problem or situation that might exist within the condensing unit. When that control board wants to turn on the condenser unit, it simply sends 24 volts down those little wires. If you turn your thermostat down far enough to signal that you want the room cooler, the thermostat sends a signal to the control board in the furnace, which then turns the blower on by the coils, and then sends the 24 volts to the condensing unit. If in fact you have "no voltage from the board to the contactor" despite you adjusting the thermostat to start the cooling cycle, then your first concern would be to understand why the board or the wires from the board aren't working properly. If, on the other hand, you mean some sort of control board within the condenser unit itself, one that acts as a second brain (third if you count the thermostat) in the system and takes into account information from within the condenser such as high and low pressure readings before sending the 24 volts along to the contactor, then sure, you might well have an issue with that particular board or the pressure sensors or perhaps a whole bunch of things. Don't know. What I do know is that if you are indeed talking about this sort of internal control within the condenser itself and when you think it should be triggering the contactor but you can't detect any juice between the internal board and the contactor, then your problem isn't the contactor. The only way you can determine whether a contactor is bad is to send 24 volts to it. If you do that but the 220 volt lines within the unit aren't energized, then it's the contactor and indeed, because contactor issues can be all about carbon buildup on the contacts, you might have the symptoms you describe. But if the contactor isn't getting the 24 volts at all, you need to look for another answer. I strongly suggest that you turn this over to a repair tech given that you're no longer talking about replacing a $12 contactor in 15 minutes. Nick in Palm Springs

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.

(Sorry for the confusion about which post to reply to - I'm not familiar with forum ettiquet and had started a new thread when I should have stuck with this one). The 24anb6 is a single stage. All conversations are centered around a 3 ton unit. The ducts are in the attic space. The original house was 1140q ft. The addition is about 488q ft. The original house (1950s) has a metal ducting trunkline system that runs in a dropped ceiling in the 12' long central hallway. The new ducting is in a jumble in the attic of the addition, with a big box thing (a baffle?) and 4.5" ducts curling around everywhere - even back to the front rooms of the original house. Apparently code has changed and new 'jumper' vents needed to be installed in all the rooms? Before that ceiling was closed up, I got a glimpse up there and noticed that it looked like and orgy of Robby the Robots - probably not the most efficient thing ever. If it's true that with the ductwork currently installed would not support a more efficient unit in the future without ripping out walls, I think this makes an even stronger case for upgrading the equipment now. (I work at home and I plan on living at this house a long, long time.). I was told when to pick out plumbing fixtures, hardware, lighting, etc...I guess expected to be told when to decide on the other choices involved. If the GC had asked, I could be looking at paying 10 or 11K for exactly what I want - a 2-stage, high-efficiency, quiet unit. Instead I'm having to choose between paying nearly 9k for stuff I don't want or - it seems from this email - paying twice for the install and associated repairs in addition to the upgrade. I'm going to push for exactly what I want. The GC is working up estimates for the Carrier Infinity 17, 19, and 21 SEER units. I have no problem paying the difference in the cost of the equipment, or even the cost the have the install done 'right', which I assume means moving the trunkline up to the attic and having a single trunkline.* I'm sure things will get sticky when we start discussing who pays for what. It would be so helpful to be able to get objective estimates from a neutral party on what the original install should have cost and what the install that I'm requesting will cost. Is that ever done? I'll post any progress as it happens. Thank so much for your feedback. It has so helpful in getting clarity on this situation! ************ *The email I received this morning regarding my request to move forward with the estimates for the 17, 19 and 21 seer units: "The 17,19,21 Seer units besides being even more expensive will likely require more duct replacement, more sheetrock removal, etc. as this will snowball the work; time frame would increase accordingly. " and "Regarding the duct work replacement, it should be noted that the metal ducting trunkline system & some ducting that pre-existed in your home is still in place & that airflow supply system may need to be upsized as well, as the Seer rating increases, expanding the scope of other sheetrock & installation repairs as well." It would seem that he really doesn't want me to upgrade...From what I can gather the difference in cost of the equipment between the builder-grade Comfort series and the Infinity series is about $1,500 - about 1% of the total project cost.

Extremely unlikely because as the guy said... eventually the unit starts and runs fine. Voltage drop = no run. "If voltage drop occurred while unit was running... it would not stay running." No where does OP say anything about unit cutting out while after starting and running. You have to know what you are talking about to come to such conclusions. LOL. Does a car keep running if there is no gas? Can a car be hard to start, but then run fine once started? Yeah ok, common sense. While a car is a poor comparison more people understand the operation of a car than anything else I could use as an example. voltage drops tend to stay, not magically disappear and reappear. But thanks for playing.... In over 22 years of diagnosing only 1 voltage drop problem... if you have a voltage drop you will know it quite easily. (More complex problems in regards to start up? Uh no. Guess again and again and again.) More common to drop a leg from the pole... while also rare that's happened about half dozen times in 22 years of running service. Central AC Unit won't start with only 120v available, that confuses people because some things inside the house will still operate normally as long as it doesn't require the full 240v to operate. In Vegas, they give you odds... in a forum board that's also what I give. Magic 8 ball --- out.