Upon arrival found thermostat set to 65 F degrees. Advised customer to keep thermostat set between 70-74 F degrees. Inspected champion air handler in the attic. Blower motor is on/ running. Notice ice build up on line set. Open up cabinet of air handler to found coil frozen solid. Open return cabinet @ unit to find filter dirty. Customer also had filter @ grill. Customer remove screws and stamp face filter grill to install his own filter. Advised customer to upgrade filter grill to filter back grill to make removing and installing filter easier. 14x30 filter grill or to keep 20x20x1 filter @ equipment. Both filter is not needed, double filter will cause a restriction within the system. Follow up is needed once evaporator coil has been thawed. Need to run diagnostic to determine cause of why system is freezing up. **Put system in a state of defrost. Thermostat was put to fan On. Thermostat not calling for AC/ Cooling. Disconnect was turned off. Office to coordinate with customer for re