Had two service calls a couple of days ago, same thing happened at both of them. Customer's thought they could fix their own furnaces. The first guy had come into our shop in the morning and purchased some pressure switches for his furnace. Later that afternoon I get the call to go and look at the furnace. I show up, check the operation and found the ignitor was bad. The LED's on the circuit board told me what the problem was. Not sure why the customer thought it was the pressure switches, but he wasn't even close.(guess he has some spare pressure switches for his furnace, because they go out all the time) Later that same day, I show up at a different house to find the secondary side of the trasformer was bad. After talking to the customer, I found out they had replaced the thermostat hoping to fix it.(because as we all know, it's always the thermostat) The point I'm trying to make is that some of you think we,(the pros) are giving you a hard time by telling you to when you're having problems. Yes, some of you may be mechanically inclined, but if you don't know the basic methods of troubleshooting, you're probably not going to fix it yourself. Both of these examples show how these customers actually spent more money trying to fix it themselves, than it would have cost to just have a pro come out first. Just some food for thought.