Air Conditioners – Need for an Air Conditioner Filter

I have the same filter location as referenced by Steve Armstrong. There is no slot for the filter but it is just held in place over the return duct by a metal arm.

Here is the opening between the return and the blower: alt text http://serverintellect.jeffwids.com/public/20100802_762_furnace_filter.jpg

And here is the filter in place over that opening with the metal arm holding it in place: alt text http://serverintellect.jeffwids.com/public/20100802_762_furnace_filter_2.jpg

I would not have known a filter was supposed to go there if there hadn't been one there already.

According to this, the Frigidaire FAS182H2A1 is an 18000 BTU device.
http://www.appliancepartsnationwide.com/FAS182H2A1/53279.htm

That's pretty powerful if working properly. The government suggests 8000 BTU for 325 SF.

http://www.energystar.gov/index.cfm?c=roomac.pr_properly_sized

Check your outside coils too and clean if needed. If that is not a problem it could be something internal. Some examples:

1. partial clog in your expansion valve.
2. low freon level

If cleaning the outside coils doesn't work, I do not expect repair to be practical. You can buy a new 10,000 BTU unit from Home Depot for $300. It would be reasonable to ask the owner to pay for it.