I was at my sister's house when she asked me to change her AC filter. She had replacement filters in the basement where the unit is located.
Her AC unit was replaced about 3 years ago. The duct work looks like a very custom job. The slot cover for the filters has 14x25 and an arrow for airflow. The filters she has are 14x24 and she said that the guy that installed the unit had told her what size to buy.
She has been using filters that are 1" too small for 3 years and there are no factory filters that size that I can find locally.
I am sure there is a ton of crude in the unit. What is the best solution for this problem?