It is a good practice to change your furnace filter at the beginning of each season. Unlike many furnaces that use a box type filter, older mobile homes usually have a foam or mesh type filter without a frame. The filter is normally held in place by long wires criss-crossing the inside of the filter panel or across the filter. Replacing a furnace filter in an old mobile home requires cutting the filter to size yourself.
Turn down the thermostat and wait for the furnace to shut off.
Remove the front access panel to the furnace. The access panel usually lifts up and away from the furnace. The filter is either on the back of the panel or on the furnace directly behind the panel access. Purchase a filter material that is the same as the current filter. It is either a black foam much like a window air conditioner filter or a blue mesh.
Pull off the wire rods securing the filter. The rod ends simply bend behind the edge of the access panel or in the filter housing frame. Pull the old filter out of the furnace.
Place the old filter on top of the new one and cut the new filter to the same size with a pair of household scissors.
Set the new filter either in the back of the door panel or in the filter frame housing. There is no back and front to this type of filter. Place the rod ends back under the edges of the panel or frame.
Lift the access panel and place it in the groove on the front of the furnace. Slide it down and allow it to rest on the bottom catch lip. Turn your thermostat up to the desired temperature.