Article 4. Vacuum Brakes of California Vehicle Code >> Division 12. >> Chapter 3. >> Article 4.

Motor vehicles required to be equipped with power brakes and which are equipped with vacuum or vacuum-assisted brakes shall be equipped with a properly maintained vacuum gauge of reliable and satisfactory construction, accurate within 10 percent of the actual vacuum in the supply reservoir, and visible and legible to the driver at all times. This section shall not apply to a two-axle motor truck operated singly.

Motor vehicles required to be equipped with power brakes and equipped with vacuum or vacuum-assisted brakes and motor vehicles used to tow vehicles equipped with vacuum brakes or vacuum-assisted brakes shall be equipped with either an audible or visible warning signal to indicate readily to the driver when the vacuum drops to eight inches of mercury and less. A vacuum gauge shall not be deemed to meet this requirement. This section shall not apply to a two-axle motor truck operated singly nor to any motor vehicle manufactured prior to 1964.

Vehicles required to be equipped with power brakes and equipped with vacuum or vacuum-assisted brakes shall have a check valve installed and properly maintained in the vacuum system between the source of vacuum and the vacuum reserve.