Electric seat adjustment
Adjustment of the seat is achieved by using a number of motors to allow positioning of different parts of the seat. Movement is possible in the following ways.
- Front to rear.
- Cushion height rear.
- Cushion height front.
- Backrest tilt.
- Headrest height.
- Lumber support.
Many vehicles have electric adjustment of mirrors, particularly on the passenger side. The system used is much the same as has been discussed above in relation to seat movement. Two small motors are used to move the mirror vertically or horizontally. Many mirrors also contain a small heating element on the rear of the glass. This is operated for a few minutes when the ignition is first switched on and can also be linked to the heated rear window circuit. Electrically operated mirror circuit, which includes feedback resistors for positional memory.
Electric sun-roof operation
The operation of an electric sun-roof is similar to the motor reverse circuit discussed earlier in this chapter. However, further components and circuitry are needed to allow the roof to slide, tilt and stop in the closed position. The extra components used are a micro switch and a latching relay. A latching relay works in much the same way as a normal relay except that it locks into position each time it is energized. The mechanism used to achieve this is much like that used in ball-point pens that use a button on top.
Door locking circuit
When the key is turned in the driver’s door lock, all the other doors on the vehicle should also lock. Motors or solenoids in each door achieve this. If the system can only be operated from the driver’s door key, then an actuator is not required in this door. If the system can be operated from either front door or by remote control, then all the doors need an actuator. Vehicles with sophisticated alarm systems often lock all the doors as the alarm is set.
Electric window operation
The basic form of electric window operation is similar to many of the systems discussed so far in this chapter; that is, a motor reversing system that is operated either by relays or directly by a switch. More sophisticated systems are now becoming more popular for reasons of safety as well as improved comfort. The following features are now available from many manufacturers:
- O ne shot up or down.
- Inch up or down.
- Lazy lock.
Adaptive cruise control
Conventional cruise control has now developed to a high degree of quality. It is, however, not always very practical on many European roads as the speed of the general traffic varies constantly and traffic is often very heavy. The driver has to take over from the cruise control system on many occasions to speed up or slow down. Adaptive cruise control can automatically adjust the vehicle speed to the current traffic situation.
Clutch or automatic gearbox switch
The clutch switch is fitted in a similar manner to the brake switch. It deactivates the cruise system to prevent the engine speed increasing if the clutch is pressed. The automatic gearbox switch will only allow the cruise to be engaged when it is in the ‘drive’ position. This is again to prevent the engine over-speeding if the cruise control tried to accelerate to a high road speed with the gear selector in the ‘1’ or ‘2’ position. The gearbox will still change gear if accelerating back up to a set speed as long as it ‘knows’ top gear is available.
When the remote key is operated (by pressing a small switch), a complex code is transmitted. The number of codes used is in excess of 50 000. The receiver sensor picks up this code and sends it in an electrical form to the main control unit. If the received code is correct, the relays are triggered and the doors are either locked or unlocked. On some systems, if an incorrect code is received on three consecutive occasions when attempting to unlock the doors, the system will switch itself off until the door is opened by the key.