Furnace tune ups should take anywhere from 45 minutes to hour and a half, depending on what the technician has to deal with when he gets there. I was a heating and AC professional for over 10 years and I had tune ups that only took me 30 minutes, and others where it seemed like I had to practically disassemble the entire furnace, clean, then put back together. Every call is unique. However, it's important you trust your contractor. Your instincts are more accurate than you probably give yourself credit for. I don't remember a tune up ever going less than a 1/2 hr in my 10 years of experience. It just takes time to setup, take down, and perform the actual maintenance. If you figure a minute per inspection point, it should have at least taken half an hr. I've showed up to furnaces that look flawless, and I still take them apart and clean them because that's what the homeowner paid me for. If there is even a hint of a cracked heat exchanger, get a second opinion. There are scams out there, and unfortunately a 20 minute inspection wouldn't reveal that. Have whomever is making the claim show you via camera or by physically removing the combustion chamber from the furnace and showing you. As weird as that sounds, I've removed heat exchangers out of furnaces just to prove that there was an issue. A cracked combustion chamber can be a serious issue, so the fact that he said it should be fine says either he doesn't know what he's doing or he's not being truthful, or both. It's not that cracked heat exchangers are leaking carbon monoxide, it's that they can. It's the potential that makes it dangerous. Hope this helps!
Yes. You should expect to pay a diagnostic fee to cover the cost of the technician's visit, the diagnosis of your air conditioner's problem, and a quote for the repair options. You will be advised of the issue along with recommended options to correct it, which may include a system replacement if your unit is old or significantly damaged. If you decide to replace the system, the diagnostic fee will be credited toward your replacement purchase.