There are two types of "doors" (really just a plastic flap) in an AC system, the "temperature blend door" and a "mode" door. Temp blend doors are in the heater box, and direct incoming air from the blower fan over either the heater core or AC coil, depending on what you select. When the actuator for the temp door fails, the door remains "stuck" either on heat or cold. A mode door, or doors (there can be more than one) is used to direct air to various vents or outside air. When an actuator fails, it would be highly unusual for it to start working again, so I doubt your problem is a caused by a failed actuator for any of these doors. One of the simplest causes for an AC system that sometimes works and sometimes doesn't is that it is low on refrigerant. Try to gauge when the compressor is working. If it constantly cycling on and off, then it is low on r134a. To recharge it, don't waste your time and money on those "AC Pro" kits, they add a "stop leak" gunk to the system and if the system does have a leak, you'll just be wasting money trying to recharge it. Take it to a shop and have it tested for a leak, then recharged. Do that first before tearing into a dash looking for a broken blend or more door.
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