C1256 low pressure accumulator
BS accumulators are devices used for storing hydraulic pressure during the hold-release-reapply cycle. They are present in both integral and non-integral ABS systems. In integral systems, there is an electric pump that offers high-pressure power assist and also supplies pressure for the hold-release-reapply cycle. On the other hand, non-integral systems make use of a 50 psi spring-loaded accumulator to maintain pressure during the cycle.
Integral ABS units combine the master cylinder, modulator, electric pump, and accumulator into a single modular assembly. The electric pump is activated by a relay that receives a control signal from the ABS control module. These pumps generate pressure for the hold-release-reapply cycle and often support brake assist functions. The accumulator is responsible for storing pressure in the system.
These accumulators use a nitrogen gas charge separated from the pressurized hydraulic fluid by a thick rubber diaphragm. When filled with pressurized fluid from the pump, they can reach hazardous pressures and should be treated with caution. Typically, they are depressurized by pulling the relay and pumping the brake pedal 25-40 times before any maintenance work can be done. It is important to always refer to the manufacturer's service manuals and TSBs before carrying out any repairs on an ABS system.
A crucial high-pressure accumulator is equipped with both low-pressure and high-pressure switches. These switches enable the ABS control module to maintain pressure within a specific range, typically between 1000 psi and 1600 psi. If the pressure drops below this range, the control module will activate the amber ABS light. In certain cases, high-pressure accumulators can reach pressures as high as 2700 psi.
