Description and Operation Information

DESCRIPTION

The Hella system consists of the following three control groups:

^ Vacuum Control - consists of a vacuum pump, a venting safety solenoid and a diaphragm that controls the throttle linkage.

^ Electronic Control - consists of the electronic cruise control module and an engine overspeed relay.

^ Safety Control - consists of the master instrument panel control switch, switches on the steering wheel, and the brake and clutch switches.
OPERATION

Power

When the master instrument panel control switch is turned on, power is supplied to the engine overspeed relay and the cruise control module.

The overspeed relay then powers the cruise control module stop contact through the brake and clutch switches. It also powers the vacuum pump and the safety solenoid.

NOTE: The ground path for the safety solenoid and the instrument cluster indicator is provided by the cruise control module only when the vehicle is moving faster than 48 km/h (30 mph), which the module determines at the speed sensor input.
The steering wheel is equipped with two switches. One switch permits acceleration and memory storage of a vehicle speed as follows:

By pressing the "+" switch, the voltage from the control module (5 volts) passes through a resistance of 100 ohms. As long as the pressure is applied, the vehicle accelerates. Acceleration is also possible by pressing on the accelerator pedal and pressing "+" the moment the desired speed is obtained.

The information is translated by the cruise control module which keeps track of two parameters:

^ real vehicle speed as determined by the speed sensor or electronic speedometer, if equipped.

^ memory storage of the desired speed.

Continous comparison of these two speeds permits control of the vacuum pump causing a vacuum in the diaphragm assuring vehicle speed stability (the pump has a regulation solenoid).

If regulation is interrupted (pressure on the brake or clutch pedal), press R (resume) on the steering wheel switch. The voltage from the control module (5 volts) passes through a resistance of 330 ohms. The information is translated by the electronics and the vehicle automatically returns to the earlier speed stored in memory.
The other steering wheel switch interrupts speed regulation by direct grounding of the control module. The information is sent to the solenoid deceleration control terminal of the control module which turns the pump solenoid on and vents the vacuum circuit.

Safety

When the engine reaches 5,400 rpm, the over-speed relay receives enough power from the tachometer to become energized. The power supply for the cruise control module safety circuit is interrupted which causes the module to open the ground path. Since the safety solenoid and the pump are no longer operating, the vacuum circuit is inoperative. Pressure on the brake or clutch pedal will have the same result.

The stop switch also sends information to the control module. The electronics open the ground path. The safety solenoid then vents the circuit.

NOTE: It is still possible to exceed the memorized speed by pressing the accelerator. When the pedal is released, the vehicle resumes its regulated speed. The range of operation for memorization of a regulated speed is approximately 48 km/h (30 mph) to 129 km/h (80 mph).