Came out to call for a system that wasn’t heating, but now it is. Customer stated that the system wasn’t heating properly the other day, but today has been working fine but still wanted me to check it. Thermostat was already satisfied when I checked it. I went to the unit to test components after cycling it on from the thermostat. Furnace fired up with no issues. I let system run for a total of 10 minutes and the temp in the home was raised from 70 to 73. I checked amps on motors, gas pressure and even checked the condensation drain. Amps on inducer motor where within range and had no sign of going out while I was checking the system. It is a 90% furnace, and it’s likely that the system had a frozen drain line causing the system not to operate properly that was able to thaw out since it is a short run from the garage utility closet through the brick wall in the back yard. I made sure the drains were clear and I did verify that the drain was draining. System is heating properly at