I have a Trane XE80 heating unit and a Trane XL1200 central air unit. I have gas heating with force blown air venting. I switched on the heat for the first time this year and the blower motor for the heating unit and the central air unit both go on. I had a family friend who is a licensed HVAC repairman fix the unit when it had a different problem in the summer with the central air. I don't know if he did something wrong and I can't get in touch with him. When he fixed the central air in the summer I was told that since I changed the thermostat without turning off the power I blew something located in the heating unit that controls both units. He told me the part would be a couple of hundred dollars but he could reroute around it and use a simple fuse from a car which he did. Also my one thermostat controls both the heat & AC. The central air unit did not go on with the heat last year. I talked to someone and they told me that it might be in the comfort setting/mode but if it was then the central air unit would be on all the time, not just when the heat goes on. The central air unit only goes on when the heat goes on. I can hear the blower motor in the heating unit and I can hear the central air condition going on as soon as the heat goes on. When I got my first gas & electric bill they were really high compared to last year. Does anyone think that the system is working properly or is something really wrong? Thanks so much in advance for anyones help.