Apart from permitted or vintage classic cars, every vehicle on the road will have turn signals installed at the front and rear. Although they are fairly robust, they do sometimes malfunction, which causes the turn signals to blink fast or not at all.
Unlike standard headlight bulbs that output a constant light output, a turn signal flashes in a rhythmic pattern, which is made possible by running the power through a flash relay.
Therefore, the four main components that may result in the turn signals malfunctioning include the bulb, flasher relay, power and wiring. In order to help you diagnose the causes of the turn signal blinking fast, we have compiled the below list.
Table of Contents
1. Burnt Out Turn Signal Bulb
By far the most common reason for the turn signal blinking fast is that the bulb is burnt out. As turn signals operate in pairs, if one of the bulbs is blown, the flasher relay changes its cycling rate, which results in faster blinking.
We strongly recommend that you test the bulb first and examine the construction with a bright lamp for any abnormalities.
2. Faulty Turn Signal/Flasher Relay
If the turn signal is blinking fast but the bulb is good, this would lead to checking the flasher relay. This will be located either by the engine compartment near the battery or in the steering wheel column. Once you have found the relay, you will want to pull it out and check for any corrosion on the fuse or in the relay pins.
It’s fairly rare for the turn signal relay to malfunction unless the car is fairly old. If the car has been subjected to a large amount of water, it may be a likely cause. However, this would also cause a wide range of other fuses to malfunction too.
3. Poor Ground Connection
Another popular reason for the turn signal blinking faster than they should is due to a poor ground connection. To confirm that this is the case, you will want to trace the ground wire from the bulb housing to the termination point. If the connection is loose, simply tighten it and if you notice a build up of dirt, clean it up and then test the turn signals.
4. Incorrect Bulb Type
If you have recently changed the bulb, you may have accidentally installed the incorrect bulb type. Certain cars may require a higher wattage bulb in order to function correctly and this may cause the fast turn signal blinking. For example, many modern cars may have LED headlights and matching LED turn signals, which will require specific bulbs.
5. Insufficient Voltage
Although fairly rare, there could be an issue with an incorrect level of voltage to the car, which causes the blinkers to flash faster than they should.
This would be the hardest cause to diagnose and its advised that you use a multimeter for cars, which can help trace down any faulty wiring.
If the causes above don’t assist you in anyway, we strongly recommend plugging your car into a car diagnostic tool. This may uncover an unusual cause that may have taken many hours to find. 9 times out of 10, the main issue will be a faulty bulb and simply replacing it with the correct bulb type will fix the issue.