Possible circuit board and/or heat exchanger questions?
We have had several problems with our Gibson furnace this year. First of all, we had a bird nest in the blower? 2 years in a row (we finally got a $2 screen so this won't happen again). The HVAC technician cleaned out the bird in late September of this year. A couple of weeks later we started using the heat for the first time this fall and noticed that it was short-cycling. It would run for 2 minutes, turn off for 1 minute, and continue that cycle 24/7. Also, the "heat" didn't seem very hot. The house would warm to about 66-68 degrees depending on outside temp but could not get any warmer.
The HVAC technician came to our house on Monday and diagnosed the problem as a faulty circuit board. He was there about 15 minutes. He said the only other possibility was a cracked heat exchanger but knew that wasn't the problem because he wasn't detecting any CO. My dad was here at the time and told the technician that the same company had told him he needed a new circuit board a couple years ago, but it turned out his circuit board was fine and he really had needed a new igniter. So with this history, he said if the problem didn't end up being a circuit board I shouldn't have to pay for it. The technician just said don't worry, it is the circuit board.
The same technician came to our house on Wednesday to install the new circuit board and was here about 15 minutes again. He said it was fixed and when he went to leave, I asked if we could test it first. So after the furnace ran successfully for about 4-5 minutes, I thought it must be fixed. The air still didn't seem very warm, so he got his laser thermometer and measured the vents to be about 86-87 degrees and said that was normal since the ducts needed time to warm up. After he left, the furnace turned off and continued to short cycle -- 2 minutes on, 1 minute off. I called the company back and said I was still having the exact same issue.
A different technician came to the house in the afternoon, and after testing for several different problems to find out why the flame and blower kept turning off, he adjusted the gas level back to the manufacturer's setting. He said the earlier technician must not have done that when he installed the new circuit board in the morning. This did seem to fix the short-cycling problem. I was able to bring the house up to 72 degrees without the furnace turning off once. However, this technician did say that the air coming out of the heating vents did seem unusually cool considering it is a newer furnace. It is warming the house but just doesn't feel very warm like it used to. He said it could be a problem with the heat exchanger, but the only way to know that for sure was to spend several hours taking everything apart to see if there is a block in one of the parallel pipes. I said that as long as the furnace was warming the house in a reasonable amount of time that I wouldn't worry about the air not being very hot. He said that the problem is that if one of the pipes is blocked then it is a matter of time before the heat exchanger cracks, sending dangerous CO into my house. This technician was at my house for a total of about 1.5 hours.
So he went back to his office and called me later to let me know that my heat exchanger is still under warranty (10 year warranty, purchased in 2003) but only for a matter of months. It would cost me 4 hours of labor and $40 shipping. My concerns are the following: 1) How do I know if I even needed the new circuit board in the first place? When I asked the company about this, they said that the blocked heat exchanger probably ruined the circuit board and they were sure the circuit board was bad, but I don't understand why the new circuit board didn't fix my problem at all, at least not right away. When I asked them to test the old circuit board, they were very put off but agreed. 2) Is it unreasonable NOT to expect to pay for a circuit board that I was assured that I needed, or is this a standard practice? If not, how many hours of labor should I be billed for? And 3) Is it an obvious decision to replace the heat exchanger since it is dangerous when cracked and is under warranty, or does it sound like the company is using a scare tactic to get some work?
Thank you in advance for any advice!