I helped a friend with her Ducts this past summer.

Cats in the crawl space, need I say more.

The AC worked fine but after a while the on/off function started to act wonky so I replaced the wall controller in the hallway. I truly believe the controller was bad because it didn't respond when the buttons were pushed. Pretty much like a dead battery even with new batteries.

New (very basic) controller installed and the AC worked fine for the rest of the summer.

Switch to heat and everything worked fine for a week or two, then the heat wouldn't turn off. They did something to the controller until it went off. Then it wouldn't turn on when the temp was well past the cut on point. Auto/On - Fan switch works ok.

It appears to start and stop for no reason and it will heat the house to the high 70's when the controller is set to 65 and then shut off for no telling how long before it starts up again.

The other night they asked me where the circuit breaker is to shut it off. I told them not to because the heater has to cool down after the gas burners shut off and killing the power will stop the fan from cooling it down.

I understand AC/Heat to the point of cleaning and replacing parts but I have no idea where to start on a system flaking out. I told them call a full time AC/Heat guy but it bugs me to not know what is happening.

Any thoughts?