Knocking: This is an unusual symptom, but if you're experiencing this, it's almost definitely a problem with your blender actuator.
These gears are just plastic after all, and they are subject to some wear and tear at a much greater frequency than metal gears would be. If some of the teeth have worn down or broken off, then the gears will start slipping and create that bothersome sound. In most cases, you'll get this noise when there is a problem with those plastic gears inside the actuator. This will be most prominent when you turn on the AC, or try to adjust the temperature and intensity settings. Noise: If you're hearing a sort of droning or squeaking repetitive sound from somewhere within your dashboard around the Center area, in the more or less general area that you are control knobs for the HVAC system are located, that's a good sign there's something wrong with the blend door actuator. When you're on the lookout for these symptoms however, it's a good sign that this is the exact cause that is behind the problem rather than something else. There are a number of things that can potentially cause your car's air conditioning and heating to go wrong, and the blend door actuator is just one of them. Temperature control is a fairly minor system in your vehicle, but it can be finicky. When the blend door actuator in your car starts going bad, there are signs you could be on the lookout for to help you properly diagnose the problem. It's about as low-tech as your car can get, where the actual technology is in the actuator itself. It opens or closes to allow air flow in whatever direction is required. The blend door is called a door because it really is just a flat panel of plastic. There should be controlled by some plastic gears that are responsible for moving the blend door where the actuator sends the correct signals. The blend door, which the actuator controls, is what diverts and controls the flow of air. It's a very small piece of technology, you can fill it easily in your hand if you were to remove it. There are a couple of plastic gears inside, the electronics, and then the plastic case that houses the whole thing. The blend door actuator itself is a very small plastic box. Most modern vehicles have the ability for rear passengers or front passengers to alter their personal climate, which means they'll have a separate blend door actuator for controlling that. Your car may have more than one of these if you have the ability to control the temperature in different zones. This controls things like defrost as well as whether or not the air is going to come through the floor vents or the mid-level vents and so on. As you adjust the temperature up and down, or the intensity of the air flow, the signals go through the actuator. The blend door actuator is a small electric motor that features sensors connected to your car's climate control system.
Actuator is basically another word for motor.