AC Filters

[Craig]

My AC unit is missing the filters. Should I use something specific for a filter, or just stick any old AC filter material in there?

[uwe]

Hi Craig,

I used 3M A/C Filter foam on A/C before, and i also used it on my Airstream last week. It needs to have support behind it, so it will not get sucked in the intake. Other than that, it seems to work fine, and does not restrict the airflow noticeably.
It is available in hardware stores at a very low price.