Cd1403

Just replaced thermostat now drivers side blowing cold air and passenger side blowing warm.any ideas please

Need help?recently my audi a4 avant 1.9tdi Quattro sport has started too overheat.start driving and temperature goes to normal 90dg then about ten minutes later shoots up too 120dg.cant find any leaks and am not loosing any coolant fluid was thinking it could be the thermostat