11 year old Goodman - should I repair or replace?

Hello,
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-$6000 installed. Are the high-efficiency furnace and a/c units really that much more expensive and/or more involved to install - or is this place charging a premium to install the high-end components?
Thanks ahead of time for any guidance you can offer!!!
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Makes me wonder if you have a bad transformer, feeding more than 24 VAC. Shouldn't burn up boards that quickly. In any case, the wire from the thermostat oughta have a fuse in it (not provided, probably, your guy will have to put it in). Blow fuses, not boards.
I wonder about the "bad thermostat" idea. You can do a lot of really goofy things with a bad thermostat, but I doubt burn spots and such.
Sounds like some thing is shorted, but what?
As for the estimate being high, eleven grand sounds a bit much. Did you get a couple other estimates? Your old 3 ton AC was probably not moving 3 tons of heat, so please don't be in a hurry to go to a larger unit.
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Christopher A. Young
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Try telling the stupid fuck tech to use an inline fuse to trouble shoot the problem. That way the fuse will blow instead of the 170$ board.

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HA HA HA HA!!!
What dream world do you live in?
The $11,000 quote sounds about right for a basic builder-grade unit installed.
The HVAC system is your most complex and important system in your house. Don't cheap out on it.
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The second thing that came to mind. If the blower motor is shorted out, that could explain over amping, and burning out the boards. So, in addition to checking if the transformer is over volting, it's good to check if the blower motor is shorted.
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Christopher A. Young
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aka-SBM posted for all of us... I don't top post - see either inline or at bottom.

Believe me, if I could I would... really.
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Well, I'm happy to report that my a/c has been fixed. The 2nd HVAC place sent out a top-notch tech who found the problem and put in a workaround to get the unit up and running =-= all in a bit over 1 hour. The short was caused by the high-voltage and 24v power lines in the outside compressor being fused together. The covering on the wires had melted and the metal was touching.
Thank You all for feedback!
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wrote:

You have just gotten a lot of bad circuit boards. Goodman put out a huge batch of bad boards. Have your seemingly highly trained professional technician keep replacing boards. When the repair bill gets up to $11,000 then you can tell him to stop and go ahead and put in that new super- duper system. After all, it just wouldnt be practical to do more than $11,000 in repairs if you can get a new system for that amount. Dont forget to install a new digital programmable thermostat. Its almost always the thermostat. I do hope you asked your Amana chick if she was indeed an engineer? After all, you cant do an engineering analysis unless you are "board-certified". I think she is wrong about the 4 ton system. Im sure you need a 5 ton system. Bigger is always better and the bigger systems last longer. Bubba
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Thank you all for your comments. The owner of the shop that's been working on my system recommended I get an electrician to diagnose the short. I called another shop that has an electrician on staff but they thought I'd be better off with a HVAC person they have on staff who has a good electrical troubleshooting background. They're sending him on Thursday. If he can fix it, wonderful. If he can't, they say I don't have to pay for the call.
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Please suggest that he pull the blower motor out of the lower cabinet. Isolate it, and check for shorts to ground. That's a very likely cause.
And as Geo Jr and I both suggested, a fuse or two installed in the right places are cheaper than $170 boards.
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Why do you have to remove the blower from the cabinet? Honestly Stormy, let others answer service questions. You don't have enough time in the saddle.
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Respectfully, Bob

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Well, you really don't. But it only takes a couple moments to do so.
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On Sun, 20 Aug 2006 01:08:46 GMT, "Bob_Loblaw"

Because thats the only way Stormy can get to the thermostat. Bubba
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He ought to also refund your money. Period. If he doesn't have a competent tech who can troubleshoot the problem, he doesn't need to be in the service business. Further, if the tech fried the new board, he should have replaced it at his own cost. If the new board was bad, it would have been under warranty and wouldn't have cost him anything... sounds like you got a tech who doesn't know a screwdriver from a capacitor lead.
Anytime an HVAC contractor sends you to someone else, that's his way of saying, "We don't know what the F**K we are doing". At least he did you the favor of sending you else where before conning you out of even more money.

That is good customer service even before they arrive. I am sure they will either fix the problem or make proper recommendations for a new system. They will also be grateful for all your future referrals to them.
If you do end up replacing the furnace, go with Goodman and get a 95% efficient furnace. You might consider a 14 SEER heat pump and get yourself a high efficiency dual fuel system... a wise choice for southern Penn. Electric rates are reasonable and if you plan to stay in the house for at least five years, you will save quite a bit on energy both in heating and cooling season. I expect you could get a 3 or 3.5 ton heat pump, 95%, 90k or 110k btu furnace installed with all the proper controls, etc. for around $7000 if you find an honest, competent company to bid the job. The system will also qualify for federal tax credit.
Goodman has redesigned their systems and have done a good job of it. It is reasonably priced equipment with a good warranty. www.goodmanmfg.com They also make Amana, same quality with a little higher price tag.... as for your 11 year old Janitrol, we'll leave that quality issue alone.
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Myhvacisdead wrote:

That's a good deal.
Your original contractor is screwing you over if they charge you for more than one replacement board. It is THEIR problem to locate and fix the short, not just keep changing parts..... what a hack!
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HVAC-Talk . com
They love to answer questions like this!

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Thanks. I'm checking this out now.
And thanks for all the other comments. I figured I was on the hook for one board but not both. I'm extra confident in that idea now.
tech wrote:

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wrote:

If you had any balls you would not need to get assurances from people you don't even know off the internet. Grow a pair man!
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wrote:

You're on the hook for ONE board only AFTER they install one that doesnt burn up. Id be checking elsewhere. Bubba

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