Arrived on site and met up with Brent my pint of contact. Was directed to Bard unit. Customer complaint is that it would run for a few seconds and shut off. Hooked up refrigerant probes to check pressures. While removing service valve cap on discharge line I noticed a hissing. Bad schrader core on service valve leaking heavily. Replaced schrader. Hooked up and found unit had 39 psi standing pressure. Unit was running and kicking out on LPS low pressure safety. Charged for not up with 4.5 lbs customer supplied 410A. Unit holds 5 lbs. Verified operations and found thermostat set to cooling but unit was heating. Incorrect wiring of control wires to thermostat and unit. Rewired unit. Verified operations.