Hi, I have a ac/heat pump unit, that lately is acting like it is possessed. We will turn it on one time and everything will work just fine. But then after we turn it off for awhile when we turn it back on the unit outside will start up, but the blower inside won't work. If you then turn it off and turn the heat on it will be fine. When we try to turn just the fan on, nothing happens. It has also done this sometimes when we turn the heat on, it won't work then we will switch to the air and its fine. It seems to know when it's the hottest day no air, or the coldest day no heat. I just had the unit looked at 4 months ago and then everything was OK, except that the tech said my thermostat was out dated and that I should switch to a digital one. The unit is about 12 years old. If it is the thermostat how do I tell, can I fix it myself. Thanks

You may have a bad blower relay or bad thermostat. When your blower is not coming on you can remove the thermostat cover and jumper the terminales R and G with a small wire, if the blower doesn't come on its not the thermostat. It's a bad blower relay, blower time delay or control board depends on what you have.

Without knowing the make a model unit you are talking about it is hard to guess what the problem might be, but with that said, yes, it could be the thermostat. Many units use the thermostat to control the air handler fan. If the thermostat relay that controls the fan is going bad it could keep the fan from getting the thermostat signal.

Eric D