The thermostat wires hooked to the unit is a five wire plug in type but someone changed the thermostat and it has places for many more wires. They removed the plug and connect to wires together. The cooling mode works just fine. Do I need to get a 5 wire thermostat? My heat pump is a Friedrich Vert-I-Pak model vha18k50rtd.
You will also need the wiring diagram of the thermostat (available on line from it's manufacturer). These instructions are simple and easy to verify that your thermostat is compatible, and wired correctly. You haven't stated who changed the thermostat, or why. You might want to begin by answering these questions.
