Performed 1 system cooling diagnostics. Customer has stated that system was freezing up and not cooling home. Tech found collapsed return duct. Tech fixed duct. Tech ran system and found that system was low on refrigerant due to refrigerant leak. With customers approval tech added missing refrigerant and signed them up for the maintenance program to monitor refrigerant leak. Tech advised homeowner that adding missing refrigerant is only a temporary solution and refrigerant will continue to leak out at an unknown rate. Customer has setup time with a comfort advisor to to pricing on a new hvac system. System was operating and cooling at the end of service call. Advised homeowner that we can also perform leak search at additional cost at his maintenance visit and provide an additional estimate once the leak had been found.