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Your Indicator relay (flasher unit) worn out? » Read more about common malfunctions • Repair • Replacement manual
Impulse generator for signalling system: the indicator flasher relay
The indicator flasher relay is a traditional car component and has been in use since decades, precisely regulating the turn indicator's signalling system. The typical flashing enhances the signalling effect of the yellow lights on both sides of the car. In case of failure, a new flasher relay as a component is easy to find and to replace.
Indicator relay functions
Operation the turn indicator is just one of the relay's functions. It reliably fulfills three tasks:
- regulating the turn signal frequency
- operating all blinkers simultaneously in case of emergency
- signalling a defective bulb.
The turn indicators are fixed on the car's front wings. When changing direction on crossroads, motorway exits and entries, T-junctions, the driver is obliged to announce his intended change of direction to the other traffic participants by switching on the turn indicator with the turn signal lever. The indicator flasher relay switches the characteristic ½ second per cycle frequency. The warning flasher function serves as emergency signalling. A simple pressure switch activates all of the car's blinkers when pressed, enabling incapacitated or accident cars to make themselves seen. In risky situations, e.g. in case of a traffic congestion, the flashing signal can be used to alert the rear traffic on the motorway to slow down. Relatively unknown is the third function of the turn indicator relay. It warns for a defective bulb by changing its signal frequency. If the turn indicator is activated on the side of the defective bulb, the frequency doubles. This is clearly visible and audible for the driver, enabling him to quickly identify and repair the defective lamp.
Turn indicator relay defects
The accelerated flashing signal does not indicate a defective flasher relay. In this case, the relay functions correctly and the fault lies with the bulb. A defective relay does not initiate any signal at all. It is an electromechanical component, which can burn out as a result of penetrating moist or voltage peaks. Repair is usually not possible and never recommended. The component is easy to find and to replace.
Flasher relay: installation, location and repair
The turn indicator flasher relay is usually located in the fuse box. A car has several relays installed and therefore it is important to be certain about the exact location. It is a small, black cube connected to a socket with plug contacts. The fuse box cover provides information which relay is responsible for the turn indicator signal. Its repair is just as easy: the relay is pulled out and the spare part is inserted in the same place – done. Nevertheless, the turn indicator flasher relay is a safety-relevant component. If a defect occurs and no garage is in the neighbourhood, a little trick might help: The relay unit is removed and opened. The actual relay sits in another cube, soldered on the component's circuit board. Being an electromechanical component, it is possibly just jammed. Knocking a few times on the actual relay could help here. With a bit of luck, the jamming is loosened and the relay functions normally for now. Another tip for removing the relay: the exact position can be found in the operation manual under "fuses". It is usually installed in proximity of the fuse box or the control unit. Alternatively, it can have a totally different location, e.g. behind a switch. If the unit has to be removed from the dashboard, there is a considerable risk of scratching the cover as well as the dashboard. An ice scraper can assist removing the turn indicator flasher relay without damage.
Buying a flasher relay
A new turn indicator flasher relay costs between 10 and 40 EUR ( ±£9 - £36) at most. Make sure it is a branded quality component to ensure its lasting operation. If a relay fails untimely, the car should be checked on faulty current. In the worst case, an unidentified source of voltage peaks can lead to cable fire. Therefore a cause investigation is always part of a failing turn indicator flasher relay.