3 Symptoms of a Malfunctioning or Faulty Hazard/Indicator Relay

The hazard and indicator lights on the vast majority of road vehicles are controlled by a relay, also referred to as a flasher.

The relay is an electrical device that controls the lighting by acting as a switch. According on the vehicle's specific needs, they come in a range of shapes, sizes, and designs when current is given to the relay, the circuit within cuts on and off, resulting in the relay clicking sound and the turn signal or danger lights blinking.

While flashers are a basic component in both design and function, they play a significant part in a vehicle's overall driveability and can jeopardise safety if they fail. If you check MOT history of your vehicle and realise a previous MOT failed due to the lights not working, there could be two reasons for this. Either the bulb(s) had blown, or it was a faulty relay. To confirm this go through any previous repair invoices (if available).

Are you aware that, according to an online MOT history checker, one of the most prevalent reasons for a MOT test failure is the lights? The bulbs in your cars high and low beams, left/right indicators, hazards, and other lights may need to be replaced.

A faulty or malfunctioning flasher relay usually causes a few indications that warn the motorist to a possible problem. A few signs are as follows:

1.      Hazards or indicator lights don't work - The most typical indication of a defective or faulty flasher relay is the absence of hazards or indicator lights. When the indicator lever or hazard light button is pressed, the relay can break or have internal issues, causing the lights to malfunction or not respond at all. While this is unlikely to affect engine performance, it will leave the vehicle without working hazard lights and, more crucially, indicators, which can be dangerous. This is why you should check MOT status and have the problem fixed to avoid a failure. This could also be something simple as a blown bulb.

2.      Hazards or indicator lights remain on - Hazards or indicator lights that remain on are another sign of a malfunctioning flasher relay. When the hazards or indicators are engaged, if the relay has an internal short circuit, the hazards or indicators may stay on instead of flashing. While the lights may continue to light, they will no longer be able to signal a turn or warn other motorists of an emergency incident. Electrical faults can generate similar symptoms, so getting your car correctly examined by a car mechanic is essential.

3.      Additional lights aren't functioning - Along with your hazards; you could notice that other lights, such as headlights, daytime running lights, and even brake lights, aren't working. Other lights may be wired via or with the relay on some cars, causing a problem if the flasher relay fails. If you look online for 'check my MOT history' and discover that your car previously failed the MOT test due to the lights not working, the relay or something as simple as a burnt-out bulb might be to blame.

While faults with the indicator/hazard relay usually do not impede the vehicle's ability to drive, they might present issues that threaten visibility and safety. While flasher relays are not sophisticated components, because to the very convoluted structure of electrical systems, they can be difficult to diagnose. Whether you suspect a problem with your vehicle's relay or not sure if a bulb has blown out, get it diagnosed by a skilled technician to see if the relay needs to be replaced.

How can you know whether an indicator light is turned on?

The simplest way to test the indicators is to turn on the hazard lights. After turning on the hazard lights exit the car and double-check that all six lights are working. Your car has two in the front and back, as well as one on each side (front wings). Remember, you don't have to start the engine to answer this question, simply switch on the ignition.