Headlight beam setting

9.4.3 Headlight beam setting

Figure 9.13 Principle of a beam setter

Many types of beam setting equipment are avail- able and most work on the same principle. This is represented by Figure 9.13. The method is

for every 1 m the car is away from the board*. the same as using an aiming board but is more The break-off point should be adjusted to the convenient and accurate due to easier working centre line of each light in turn. and because less room is required. To set the

headlights of a car using an aiming board the fol- Note: If the required dip is 1% then 1 cm per lowing procedure should be adopted.

1 m. If 1.2% is required then 1.2 cm per 1 m, etc.

1. Park the car on level ground square on to a vertical aiming board at a distance of 10 m if possible. The car should be unladen except for

9.5 Auxiliaries

the driver.

2. Mark out the aiming board as shown in Figure 9.14.

9.5.1 Wiper motors and linkages

3. Bounce the suspension to ensure it is level. Most wiper linkages consist of series or parallel

4. With the lights set on dip beam, adjust the cut- mechanisms. Some older types use a flexible off line to the horizontal mark, which will be

rack and wheel boxes similar to the operating

1 cm below the height of the headlight centre mechanism of many sunroofs. One of the main

210 Advanced automotive fault diagnosis

Figure 9.14 Headlight aiming board (Europe RHD)

Figure 9.15 Interesting headlights on the new Jaguar S-type

considerations for the design of a wiper linkage to each other. For a fast speed the third brush is is the point at which the blades must reverse.

placed closer to the earth brush. This reduces the This is because of the high forces on the motor

number of armature windings between them, and linkage at this time. If the reverse point is set

which reduces resistance hence increasing cur- so that the linkage is at its maximum force trans-

rent and therefore speed. Figure 9.17 shows two mission angle then the reverse action of the

typical wiper motors. Typical specifications for blades puts less strain on the system. This also

wiper motor speed and hence wipe frequency are ensures smoother operation. Figure 9.16 shows a

45 rev/min at normal speed and 65 rev/min at fast typical wiper linkage layout.

speed. The motor must be able to overcome the Most if not all wiper motors now in use are

starting friction of each blade at a minimum speed permanent magnet motors. The drive is taken via

of 5 rev/min.

a worm gear to increase torque and reduce speed. The wiper motor or the associated circuit often Three brushes may be used to allow two-speed

has some kind of short circuit protection. This is operation. The normal speed operates through two

to protect the motor in the event of stalling, if brushes placed in the usual positions opposite

frozen to the screen for example. A thermal trip

Electrical systems 211

of some type is often used or a current sensing onto an appropriate part of the screen by two or circuit in the wiper ECU if fitted. The maximum

more jets. A non-return valve is often fitted in the time a motor can withstand stalled current is nor-

line to the jets to prevent water siphoning back to mally specified. This is usually in the region of

the reservoir. This also allows ‘instant’ operation about 15 minutes.

when the washer button is pressed. The washer The windscreen washer system usually con-

circuit is normally linked in to the wiper circuit sists of a simple DC permanent magnet motor

such that when the washers are operated the wipers driving a centrifugal water pump. The water,

start automatically and will continue for several preferably with a cleaning additive, is directed

more sweeps after the washers have stopped.