Question about air-conditioner

今天早上收到房客的e-mail,他说，we are having trouble with the thermostat.  It gets stuck all the time.  It continues to run when you turn it off.  It's been on A/C for the last two days and nights...
于是我叫他把fan关上，他又来e-mail说，We did.  It stayed on all morning...62 in the house...I just turned off the breaker.
我不明白，明明是开暖气，怎么变成开空调(冷气)了?有人知道这是怎么回事吗? 这是个13年新的singlefamilyhouse,中央空调。本应该亲自去一趟看看，可是这房子离我家100miles，有点远。先谢谢!