Came out to call for a furnace not heating properly. Renter stated that the home wasn’t getting warm and the system was shutting off before the thermostat was satisfied. I checked system over and found the furnace reading a limit code. High limit switch is tripping. I checked filter and found it needed to be changed. The systems return grill is low to the floor and pretty small. It’s an 8x24 and isnt pulling enough cfm to help heat the home properly, especially in these temperatures. I tested systems gas pressure, amps, and temperatures to verify the furnace is operating properly. Gas pressure was a little high, so I adjusted it from 3.9 to 3.5 recommended setting. Flame sensor was dirty also, so I cleaned it. Overall system needs more return air to help heat and cool the home better. I recommended increasing 8x24 grill to a 10x24 and cutting in a 12x24 in bedroom by closet for more airflow. System cycled off at 68 degrees set on thermostat.