I have a 11 year old Goodman gas furnace (model gmp125-5) with a 3 ton central air unit (southern Pennsylvania). The a/c quit working a few weeks ago. I had a serviceman come out and he said the control board had burn spots on it. He put in a new control board, turned on the system, it ran for about 1 minute and then burnt up the replacement board. I was told that the thermostat (basic round dial one) could be causing a short so I put in a digital programmable thermostat. They put in a second control board. The tech was going to turn on the a/c again and I said let's just turn the blower fan from auto to on first and see how that works. We did that and the control board burnt out again after 1/2 minute or so. He tested the wires from the thermostat to the control board and there was no short in them.
The control boards are $170 each and my repair bill so far is close to $500. I've called several hvac shops in the area and the general concensus is that troubleshooting a short in the system could be quite costly and considering the system is 11 years old, it would be better to replace it. Thoughts/Comments?
My second question is this: How much should it cost (ballpark) for a new natural gas furnace and central air system? My house is ~2600 sq ft, 2 floors. I had an Amana supplier come out and do a engineering analysis. She said the 3 ton a/c unit is too small for my house and that I should have a 4 ton unit. She gave me quotes on new systems and I'm in shock at the price quotes, which range from $6500 for a system with the cheapest parts (13 seer a/c with 5 yr compressor warranty, 80% gas furnace) all the way to $11,000 for a 16 seer a/c with lifetime compressor/10 yr parts and a 96% gas furnace with variable speed blower and lifetime heat exchanger.
I was hoping I could get a efficient system for $5000-$6000 installed. Are the high-efficiency furnace and a/c units really that much more expensive and/or more involved to install - or is this place charging a premium to install the high-end components?
Thanks ahead of time for any guidance you can offer!!!