DIESEL LOCO - Twin Beam Head Light

DIESEL LOCO - Twin Beam Head Light

On WDG3A loco two head lights are provided on each side of Loco viz. short hood and long hood. HLB (head light circuit breaker) is provided on front panel. Head light rotating switch is provided on both control stand having 6 positions. To glow head light following switches should be in on position

1. Battery knife switch (BS)
2. Main battery circuit breaker (MB1)
3. Control circuit breaker (MB2)
4. Head light circuit breaker(HLB)


There are two bulbs in twin beam head light and in each bulb two filaments are provided. The rating of these filaments is 24V and 90W, 100W respectively. One DC-DC converter unit is provided in loco pilot cab to convert 74V DC supply in 24V DC. In this unit two DC-DC converters are provided. One program switch having 2 positions is provided on this unit.

• Position No.1- For converter No.1 
• Position No.2- For converter No.2 

Note –

1. When any of head light rotating switch is put ON then ensure that Head light will glow with respect to its position.
2. If head light is not working then change the position of Converter Program switch.
3. Follow traffic rules while working loco with head light not working.

Flasher Light 

Two flasher lights are provided on each side, one near short hood head light and other near long hood head light. Individual control box is provided for each side flasher light.

 Control box provided on right control stand is for short hood side flasher light and on left control stand for long hood side control stand.

Each control box has two toggle switches.

1. Main switch - two positions (on & off)
2. Filament switch - Two positions (F1 & F2)
3. To glow Flasher light following switches/breakers should be in ‘ON’ position.
4. Battery knife switch (BS)
5. Main battery circuit breaker (MB1)
6. Control circuit breaker (MB2)
7. Flasher light control box (Main switch) 8. Flasher light control box Filament switch (F1 / F2)

Auto Flasher Light 

This modification is done to facilitate loco pilots and assistant loco pilots however in abnormal condition both the crews are bounded to do there duty as per GR & SR rule.

 In diesel loco some changes in pneumatic (BP charging) and electrical control circuit is carried out in modified AFL.

 Whenever A-9 handle in release condition , RH is in forward or reverse direction and BP/vacuum drops in any reason, such as hose pipe uncoupled/ load part/ ACP or emergency brake applied by guard, Auto flasher light will glow automatically with following indication –

1. LED lamp will glow.
2. Buzzer sounding on control unit.
3. Engine speed comes to idle.

 When flasher light glows automatically then SW1/SW2 push button is provided on both control stands to turn off it. While pressing SW1/SW2, AFL will extinguish and buzzer will stop, but LED does not extinguish till BP will not recharged up to 4.7 kg/cm2. Before pressing SW1/SW2 switch, keep ‘ON’ the manual flasher light switch.

While working train if AFL glows automatically, LED glows, buzzer sounds and engine speed comes on idle that time loco pilot should take this incident as an abnormal condition and work as per GR&SR rules.

PR-1 relay (60 sec. time delay relay) is provided in a circuit to avoid the glowing of AFL on releasing of A9 after breaking. AFL will glow automatically if BP will not restore to 4.7 kg/cm2 within 60 seconds after releasing A9.

 Normally BP charging takes place through 5.5 mm diameter choke, it is fitted between MR-2 and ad
ditional C2 relay valve. Initially or while recharging BP after application, the charging rate of BP is very slow through this chock therefore SP1 & SP2 switches are provide on both control stand for quick charging of BP. Whenever this push button is pressed a magnet valve will energize and BP will charged through 19 mm chock.

Loco pilot should ensure the working of Auto Flasher Light while taking charge.

Trouble Shooting of Auto Flasher Light 

1. Auto flasher light glow without effecting engine speed – it means FLR is defective, wedge it in energize condition.

2. Auto flasher light is glowing and engine speed not increasing –
A) If PR3 is defective (energized), remove one wire of P2 and tape it.
B) If PCS-1 is defective, short it.

In following condition flasher light should be made ON immediately

1. Sudden drop of vacuum / BP or fluctuation in AFI.
2. Sudden experience of jerk / lurch.
3. When noticed rail fracture / weld fracture.
4. Train parting.
5. Loco failed.
6. Derailment.
7. When opposite line is required to protect.

 Marker Light

 Two marker lights are provided on each side of Loco viz. short hood and long hood. Marker light gets supply from battery / auxiliary generator. To glow Marker light following switches/ circuit breakers should be in on position

1. Battery knife switch (BS)
 2. Main battery circuit breaker (MB1)
3. Control circuit breaker (MB2)
4. Lighting circuit breaker
5. Toggle switch on control stand

Each marker light has two glasses one is red and other is white colour, it can be changed by slider knob. To work light engine put front side white glass and rear side red.

 Note- Some loco fitted with LED type marker light.