Thanks mike_home. Glad to know that even the pros might have struggled with this problem. Adding the C wire was not a necessity, although it did fix the secondary problem (installing new batteries presumably would have done the same, but the thermostat did not even show a "low battery" warning, and I did not have new batteries handy). Adding the C wire will cut down on how often I will need to replace the batteries, and if for some reason weak batteries caused the secondary problem, then I should not have to worry about that again since it is getting power from the C wire now.

Thank you so much for your replies! This quote is from Salesman #3. He is the grandson of the man who started this heating and cooling company in 1945. His dad and 3 brothers all still work there. They were voted "Contractor of the Year" in 2002 and won an "Ethical Business Award" in our area last year or the year before. I thought they would be the most expensive, so I had him come out last, but his quote is the best. (he said he could do gas heat with heat pump,but doesn't recommend it based on our cheap electric. He said you have to set a temp where heat pump turns off and gas kicks in, same as Salesman #2) Last question - Does it seem reasonable that in this area people haven't been spending the money for a higher SEER unit because we only need to cool for 3 months or so? (it takes too long to get back the initial added cost) He said there hasn't been the demand for these units in this area, but I wonder if the stimulus rebate changes that. The $1500 rebate is pretty new, do they just need some time to catch up? Is it worth pushing him to quote me something from Rheem that does qualify? From what I can see on the Rheem website they have a 3 ton system that qualifies, in their high-end systems. It has lots of "bells and whistles" and I can't tell how much more it will cost. This contractor has said that he prefers to "keep it simple". less areas to have problems down the line. Do you think it is worth pursuing this in light of the new rebate?

It is quite obvious that you are not qualified to work on a gas heating system. Don't you realize you could be endangering your life and the lives of your whole family? And all in the interest of saving a buck! Anybody stupid enough to offer you assistance in this forum should have his head examined, unless the possibility of being an accessory to the fact interests him!

Brand & model number please.