Two filters with two different jobs
Under the front edge of a hood combination sit one or two flat metal mesh panels, each of them a microwave grease filter. They catch the grease carried up in steam and smoke from the pans below, and a GE Appliances owner's manual adds a second reason for them: they keep flames from the cooking surface from reaching the inside of the unit, which is why they must always be in place when the fan runs.
The charcoal filter is a different part. It is a pad of activated carbon behind the grille across the top front of the microwave, and it exists only when the air is blown back into the kitchen rather than out of the house. GE states plainly that it cannot be cleaned and must be replaced.
Ducted to the outside
If the unit sends air up a duct through the cabinet or out through the back wall, there is no charcoal filter to change. The metal grease filters still need their monthly wash, since grease reaches the duct if they are clogged or missing.
Recirculating into the room
If the air comes back out of the grille above the door, the unit is recirculating. It then carries both kinds of filter, and it is the charcoal pad that does the work on odors.
Source: GE Appliances — Over the Range Microwave Oven Owner's Manual (LVM1335) — Grease filters must always be in place and are cleaned once a month or as needed by soaking in hot water and detergent without ammonia; the charcoal filter cannot be cleaned and is replaced when dirty, usually after 6 to 12 months; disconnect power before removing the grille
How often each one needs attention
The GE manual for one of its over-the-range models asks for the grease filters to be cleaned once a month, or as needed, and for the charcoal filter to be replaced when it is noticeably dirty or discolored, usually after 6 to 12 months depending on how much the fan is used. A household that fries often will land at the short end of both.
GE's support pages add practical signs that the charcoal pad is spent. A fresh pad looks dull and porous; one that looks shiny all over is loaded with grease. An old smell coming out of the grille, different from whatever is in the pans, means the pad has stopped trapping and started giving back.
- Grease filter due: a tacky film on the mesh, drips forming at its edge, or a month since the last wash.
- Charcoal filter due: a shiny surface, stale odors from the grille, or the 6- to 12-month mark passed.
- Write the date on a strip of tape inside the cabinet above, so the next change is not a guess.
Source: GE Appliances — Over the Range Microwave Oven Owner's Manual (LVM1335) — Grease filters must always be in place and are cleaned once a month or as needed by soaking in hot water and detergent without ammonia; the charcoal filter cannot be cleaned and is replaced when dirty, usually after 6 to 12 months; disconnect power before removing the grille; GE Appliances — Over-the-Range Microwave charcoal filter replacement — Charcoal filters are model specific; a shiny surface or odors unlike the food being cooked mean replacement; the filter sits loosely, is held by the running fan and may not cover the whole opening
Washing the metal mesh without darkening it
Slide each filter toward the back by its tab, tip it down and lift it out. GE's instruction is to soak it and then swish it around in hot water with detergent, using light brushing for grease that has worked into the mesh. Ammonia and cleaners that contain it are to be avoided because they darken the metal.
Rinse the filter, shake the water out and let it dry fully before it goes back, so water is not blown into the fan housing on the next use. While the filters are out, wipe the underside of the unit around the openings, where grease settles and the work light sits.
When a filter is bent or torn
A filter with a split in its mesh or a frame that no longer seats flat lets grease straight past it. Replace it with the part listed for the model rather than running without one; the manual treats the filters as required, not optional.
Source: GE Appliances — Over the Range Microwave Oven Owner's Manual (LVM1335) — Grease filters must always be in place and are cleaned once a month or as needed by soaking in hot water and detergent without ammonia; the charcoal filter cannot be cleaned and is replaced when dirty, usually after 6 to 12 months; disconnect power before removing the grille
Fitting a new charcoal filter
Charcoal filters are model specific, and GE lists the right part number in the owner's manual and the product specifications. Buy by that number rather than by the look of the old pad, since similar pads differ by a fraction of an inch.
Many designs hide the pad behind a grille held by screws. The same GE manual asks owners to disconnect power at the breaker or pull the plug before taking the grille off. The new pad often sits loosely at an angle and may look smaller than its compartment; GE notes that the fan holds it in place once it runs and that a pad not covering the whole opening is normal.
Have everything ready before the grille comes off, so the fan and light are without power for as short a time as possible and no screw ends up lost on the cooking surface below.
- The replacement pad, bought by the part number in the manual.
- A screwdriver that fits the grille screws, if your design uses them.
- A small tray or cup to hold the screws.
- A strip of tape and a pen to note the date of the change.
Source: GE Appliances — Over the Range Microwave Oven Owner's Manual (LVM1335) — Grease filters must always be in place and are cleaned once a month or as needed by soaking in hot water and detergent without ammonia; the charcoal filter cannot be cleaned and is replaced when dirty, usually after 6 to 12 months; disconnect power before removing the grille; GE Appliances — Over-the-Range Microwave charcoal filter replacement — Charcoal filters are model specific; a shiny surface or odors unlike the food being cooked mean replacement; the filter sits loosely, is held by the running fan and may not cover the whole opening
