12 Volt DIRECTION INDICATOR FLASHER RELAY RANGE
Direction Indicator Relay Description
Direction indicators must flash at a rate of 60 to 120 Flashes per minute to comply with UK marking and lighting regulations.
Terminal Designation in accordance with DIN 72 552
31 Common ground return line to Negative battery terminal
49 Supply Input (12v)
49a Output of first turn signal circuit (to indicator switch)
49b Output of second turn signal circuit
49c Output of third turn signal circuit
C First indicator (dash) light
C2 Second indicator (dash) light
Typical Circuit Description
Power is supplied from ignition circuit to terminal 49 of the flasher relay via a fuse.
The output terminal 49a is wired to the centre pole of the turn signal on/off/on switch.
upon activating the direction indicator switch in either direction power is then supplied to the turn signal lamps through the lamp filaments to ground return completing the circuit .
The load of the flasher lamps is sensed by the flasher control unit causing it to switch on / off successively and the turn signal lamps to flash at between 60 and 120 times per minute.
Direction Indicator Faults :
If other lamps flash dimly when indicators circuit is operating
This fault is usually caused by a high resistance to ground return due to bad earth on the flasher lamp circuit due to corrosion or poor connection. May also be caused by several other factors such as:
Indicators flash rate too fast
If the indicators flash too fast this may indicate that there is insufficient load on the direction indicator circuit.
Most vehicles use a 21 watt bulb at each main indicator lamp (front & rear) and a 5 watt bulb at the side repeater lamp.
Direction Indicator Circuit Blows Fuses
If the indicator circuit causes a fuse to blow this usually means the insulation on wiring has become damaged causing a "short to ground".
MoT Inspection of Direction Indicators
A check is carried out for :
Reference : Section 1.4 Mot inspection manual (2012)
Multitimer (modern vehicles)
Late model vehicles may use a "multi timer " unit built into the fuse board
or body control module to operate direction indicators.
The Multi timer often has several other functions related to timed circuits for example , interior light delay, alarm sounder , reverse bleeper, and windscreen wiper delay.
Diagnostic testing of Indicator Circuit on modern vehicles
Diagnostic equipment with dedicated software can be used to check the direction indicator circuit on some modern vehicles. Live data from body module can show input signal from turn signal switch ON / OFF. Component actuation can operate indicator lamps to check wiring integrity can be done with multimeter.
Requirement for direction indicators depends on vehicle first use date.
Vehicles of first use date before 1st January 1936 currently have no legal requirement to be fitted with direction indicators
Vehicles of first use date prior to 1st September 1965 may combine indicators wit stop lamps or front/rear position lamps so front indicator may flash white, rear indicator may flash red.
Vehicles of first use date after 1st April 1986 must have side repeater lamps fitted but these can be incorporated within the front direction indicator lamp if a wrap around lens is fitted so lamp is visible from side.
Semaphore indicators use an electromagnet to raise the semaphore arm which must also illuminate but does not have to flash. Many classic car owners have additional indicator lamps fitted for road safety and to protect their vehicle. The semaphore indicators can also be wired to allow to flash.