Called out today due to no cooling. Upon arrival client stated that the system was blowing hot air. They replaced the thermostat with a nest. Checked all electronics and motor components. Nest thermostat was wired incorrectly due to mismatched wires. Inside the air handler they connected orange to blue and white to orange. Outside the reversing valve was stuck in heat position. Unstuck valve by magnetizing the solenoid. Unable to check refrigerant pressures due to inoperable machine. There are tons of splices and mismatched wiring throughout the home. The thermostat wire has to be redone in order to restore proper communication. After wires have been replaced we can fully inspect the system. Office will call to schedule wire replacement. This will take two people (me and wade) about 3/4 hours. Need about 100 feet of 18/8 thermostat wire.