The cruise control vacuum bleed switch is an essential part of the cruise control system. Once you set the cruise control, the negative pressure within the vacuum is used to open and close mechanical switches. The vacuum switch located at the servo keeps a steady pressure after the cruise control is set. Once it is time to slow down, you can press the deceleration button on your steering wheel that releases the vacuum in the servo. After the vacuum is released, the vehicle automatically responds by decreasing its speed.
The vacuum supply system normally contains a one way check valve and a vacuum storage container. When the engine has low vacuum periods, the reserve vacuum supply is able to provide the extra vacuum it needs. Speed control in your vehicle is controlled by electronic signals from the cruise control module to modulate the vacuum inside the cruise servo. The cruise control servo has a vacuum diaphragm connected to a throttle lever by either a chain, cable, or linkage rod.
The cruise control vacuum bleed switch holds the vacuum in place and at the right pressure until the brake pedal is pressed down. After the brake pedal is depressed, it releases the vacuum, also known as bleeding. Sometimes the cruise control vacuum bleed switch will leak and will not stay at a set speed. If the switch will not open, the cruise control may not slow your vehicle down.
There are many parts to a vacuum run cruise control system and all of these parts need to be running properly for the cruise control to work. If the cruise control vacuum bleed switch is not working right, you may hear a hissing noise near the pedals. This part can become worn and break over time, especially if it is used on a regular basis. Because of this, you should be aware of the symptoms the cruise control vacuum bleed switch gives off before it completely fails.
Signs your cruise control vacuum bleed switch needs to be replaced includes:
- The cruise control will not set at all
- The cruise control will not hold its speed once it is set
- There is a hissing noise near the pedals
- The cruise control will not disengage when the brake pedal is pushed down
If you are experiencing any of the above symptoms, consult a professional mechanic.