I just purchased my house and noticed air flow at the intake was very low. I removed the cover and discovered that the filter was not installed. I'm not sure haw long it went without the filter. It is a Rheem criterian Air and Furnace combined. What can I do to get the air flow back to normal? I dont see another filter.

Thanks
Rick

The coil inside the air handler is very dirty. You will have to clean it very good to get the airflow back to normal. Especially th side on the return air. While at it also clean the blower wheel. When dirty the fan will be heavy and not run up to full speed