blend door problems

im haveing problem with the heater switching form the defrost to anything else and from what i can find on here it is the blend door but i cant find how to get it out to see if that is the real problem if someone could help me find out how to get to this out or of any other way to fix my problem thanks

Year of vehicle, and if it is automatic climate control or manual HVAC would be very helpful. If the HVAC system loses vacuum, it will default to defrost. Check the vacuum line from the engine to the HVAC mode switch. The line may be broken, or the reservoir may have a leak.