Thermostat When I turn my heat on my AC also turns on any ideas why?

Heat pump and AC are basically working the same principle. When you turn on the heat pump is just like to turn on the AC. The main contactor will energize to turn on the compressor. The only difference is the 3 way valve, either switching to AC mode or heat mode. It is the most commom problem for heat pump. Check the thermostat wires for heat mode and defrost control.

Is it tripping the breaker? If it is the compressor could be on the way out. Unless you have the tools you will need an AC rep are man. The heat and AC are two separate functions not related very much. When the compressor starts to go it works harder over heats draws more electricity and trips the breaker.

The heat will normally use a low speed on the fan, & the AC along with the fan switch on the thermostat will use the high speed. The thermostat turns that high speed on when there is a call for cooling & is the same switch if you were to manually turn the fan from auto to on. Try turning the fan on @ the thermostat. If it works, then replace your thermostat. If it doesn't, it could be a bad fan speed, a bad fan relay on a control board or external relay, or a loose or broken green thermostat wire.

If you have a newer style programmable thermostat there are batteries in the thermostat that need replacing. Otherwise look at the thermostat wiring. If you have a voltmeter. check for 24 volts ac on the terminal with the red wire and the one marked C. If no voltage is there either a fuse is bad or the 24 volt control transformer is bad.

could have a bad blend that controls both heat and ac

Make sure the cooling fan turns on. When the car is hot and idling and the temp gauge is high, make sure the electric cooling fan is on. If it does not come on, if you have AC, turn on the AC and see if the fan turns on. If it turns on with AC but not by itself, then the temp switch is not working. It the fan does not turn on with AC, then the fan is broken, wire broken, fuse blown.

check for sticking sequencer.

You need a "Y" terminal. "Y" is pretty standard on every heat pump. It is the wire that will energize the compressor contactor at the outdoor unit, allowing the compressor and condensor fan to run.

What are you setting the thermostat to when you turn on the AC , if you turn on the AC and the house is warm you will need to turn the AC down to a lower setting before the the AC will start up.

make sure not turned on @ tstat to man ,also were you in the heat or cool mode when this occured .