we've all seen them...

[no_1_dave]

bulb out

 

[Bug One]

Thought it usually happened when a bulb blew?

It is. However a poor connection, or fitting led bulbs can also cause it.

My 1971 beetle is exactly the same so it's hardly a modern feature.

 

[jon.bda]

New / High end?

I had a Mk1 Fiesta that did that!

Was new and high end (if it was a Ghia or an XR2) once mate!!!

 

[Shimmy]

My instructor said it occurs when a bulb was on its way out.

Guess he was half right.

 

[energy]

to cut it short the way the flasher unit works is that the power flowing through a bimetal strip inside it makes the strip bend, and this breaks the circuit, causing the indicator to switch off. As the metal strip cools, it straightens out again and makes contact, current goes through it, indicator lights, strip gets hot, it bends and repeat.

Anything that causes the amount of curent going through that strip to change (bad connection, burned bulb, or incorrect bulb) will alter the rate at which this process happens, and therefore the flashing rate. If for example you put a really powerful bulb in one of the indicators it would flash very slowly.

I'm pretty sure most modern cars don't use this any more, instead they probably use an electronic circuit since the clicking noise is now synthesised but they still flash faster when a bulb is out, this must be programmed into their function as people have become used to this behaviour to signal a burned bulb.

 

[DBT85]

LOL so true, so true.

I may or may not mutter "basic model is it?" when I see them lol.

 

[Fuzz]

It's to do with using the resistance of the load circuit which affects the voltage and thus the activation of the relay

/\ Precisely this

 

[mjt]

The best ones are when the whole cluster turns off the and reverse light goes pink when they indicate.

How these people get an MOT I'll never know.

 

[Flukester]

to cut it short the way the flasher unit works is that the power flowing through a bimetal strip inside it makes the strip bend, and this breaks the circuit, causing the indicator to switch off. As the metal strip cools, it straightens out again and makes contact, current goes through it, indicator lights, strip gets hot, it bends and repeat.

Anything that causes the amount of curent going through that strip to change (bad connection, burned bulb, or incorrect bulb) will alter the rate at which this process happens, and therefore the flashing rate. If for example you put a really powerful bulb in one of the indicators it would flash very slowly.

I'm pretty sure most modern cars don't use this any more, instead they probably use an electronic circuit since the clicking noise is now synthesised but they still flash faster when a bulb is out, this must be programmed into their function as people have become used to this behaviour to signal a burned bulb.

this man speaketh the truth ....I doubt any manu's use bimetal flashers though any more, so it's gonna be old sheds you see with the fault condition.

 

[Souleh]

Usually if its a saxo or the likes its because the owners stuck in LED indicators which will cause it too.

 

[Dr Who]

Thought it usually happened when a bulb blew?

this

 

[Vonhelmet]

It's part of the mobile disco vibe. Get it fast enough and it's like a strobe. NN-TSSSS NN-TSSSS FLASH FLASH FLASH NN-TSSSS NN-TSSSSS.

 

[adam cool dude]

Either the relay is kaput, or on the newer/high end cars, it is meant to signify that an indicator bulb is not working (either the front, side or rear).

Lol my car is 1998 and does it. A few years ago someone nice reversed into me and left without leaving a note . Smashed the whole light unit but when driving home the indicators went crazy for the broken side only. I can only presume this was because the bulb wasn't working (Well the bulb wasn't there at all it was in pieces in a plastic bag on my passenger seat).