My parents bought a Heil AC/Furnace in 2004 and it is time to change the filter. My father had been doing it but is gravely ill and doesn't remember how to do it. I looked at it and it has a bottom plate and face plate that comes off. I didn't see a filter in either one of these areas. Where is the filter located? Thanks to anyone who can help.

A lot of times the construction filter in side the furnace is remove after installation of the furnace. The system will be filtered at a return air grill. Hope your father gets better. God bless