I have a fairly new unit less than 5yrs old. After the installment i had continuous problems with the ac in which the installers had to eat the price on service because they had never completely fixed the problem over a3 yr period and say least a dozen service calls. But now my heater is not working i called same company who installed unit. They sent a tech who diagnosed the control board as being the problem. I only question this because the fan kicks on but never lights error code is pressure switch open. The tech checked the unit but never turned it on from the thermostat to try and get it to run? And then tells me is the circuit board which from my price checking is a very costly repair. I'm just wondering if and how they can say it's that with out even turning on the unit. The ac is working fine now its just the heater that isn't working. So i guess the real question is am i right to be sceptical about the diagnosis?