Arrived on site to perform diagnostic on 5 year old Rheem furnace. Homeowner states that the system is not heating correctly. It will run for about 1 or 2 minutes and then it’ll shut off. She then has to pull the thermostat off and then it’ll work for another little while. Cycled system for heat. System came on and started heating, but shut off after a short amount of time. System threw error code for high limit shutoff. Filter that was in the register was extremely dirty. Homeowner was also unaware that there was another filter inside the unit that had never been changed. Both of these filters were causing the unit to be restricted, and cut off on high limit. Removed both filters from system. Cycled system for heat. Furnace kicked on and ran normally until it reached desired setpoint. Advised replacing filters more frequently, and also removed filter from inside the unit as only one is needed. Unit does not have any condensation safety switch or surge Protection. Went over finding