Why do speedo and rev counter dials spin round on start up?

[Wacky Racer]

I have tried to google the answer without success,

On most cars and many motorbikes when you switch the ignition on, the dials spin round to maximum and bounce back to zero.

[Mr E]

One assumes some form of functional check. Or to “look cool”

Wacky Racer said:

On most cars and many motorbikes when you switch the ignition on, the dials spin round to maximum and bounce back to zero.

I have never owned a car that does this.

[swisstoni]

I’d imagine there is an amount of theatre involved.

But i suppose it also shows that they are functional, like all the other warning lights that show that they are working by briefly lighting up.

[vikingaero]

1. SportChavBruv

[anonymous-user]

Wacky Racer said:

I have tried to google the answer without success,

On most cars and many motorbikes when you switch the ignition on, the dials spin round to maximum and bounce back to zero.

It’s because they use stepper motors to drive the needles and do not know “absolute” position of the needle. They drive themselves back and forth to find the position of each stop (like a calibration process).

[AndySheff]

It's certainly just for the 'theatre' when you have a digital dash.

[Dannbodge]

Needle sweep test. Makes sure the needles are working and can do their full range of motion, maybe even a bit of a calibration?

However, it's probably now more of a "theatre" thing as others have said.

On my old E36 when you accessed the coding for the dash, it would automatically do a sweep test.

[Alex_225]

I've seen it on some cars but it's never happened in any of the cars I've owned.

Suspect mostly a gimmick although it's quite a cool one, where some are just a bit naff haha

[shed driver]

My 1973 P5B coupe does this. Then stops. I think it's unintentional, but I may market it as a "Feature"

SD.

[thewarlock]

My newest car does this. I think I read in the manual the other day, that there's an option to turn it off.

Doesn't bother me either way tbh.

[Hub]

Funkstar De Luxe said:

Wacky Racer said:

I have tried to google the answer without success,

On most cars and many motorbikes when you switch the ignition on, the dials spin round to maximum and bounce back to zero.

It’s because they use stepper motors to drive the needles and do not know “absolute” position of the needle. They drive themselves back and forth to find the position of each stop (like a calibration process).

Interesting - while I've ever owned a car that does a 'sweep', on my current car if you sit in it for 10 mins or so after you've switched it off, the dials move/flicker up and down a bit at the bottom on and off for a bit. Might be that then!

[Plymo]

Hub said:

Funkstar De Luxe said:

Wacky Racer said:

I have tried to google the answer without success,

On most cars and many motorbikes when you switch the ignition on, the dials spin round to maximum and bounce back to zero.

It’s because they use stepper motors to drive the needles and do not know “absolute” position of the needle. They drive themselves back and forth to find the position of each stop (like a calibration process).

Interesting - while I've ever owned a car that does a 'sweep', on my current car if you sit in it for 10 mins or so after you've switched it off, the dials move/flicker up and down a bit at the bottom on and off for a bit. Might be that then!

My X-type does that - for about 10 minutes after stopping you can hear some sort of "electronic" noises, then the needles flicker and then stop, and all the noises stop
A bit weird but that's good ol' British Engineering

[Axe wound]

vikingaero said:

#SportChavBruv

In an Isuzu D-Max?

[vikingaero]

Axe wound said:

vikingaero said:

#SportChavBruv

In an Isuzu D-Max?

You have to spicethe D-Max up somehow!

[SkodaIan]

In a proper pick-up, van (or indeed any well used vehicle which gets bashed about a bit), the speedo should randomly thrash up and down until you reach about 30mph, and then read normally.

Sadly these modern electronics mean we no longer have this feature of old mechanical speedometers any more........

[TopBanana101]

I thought just for show, I also get excited every time the clocks change in a merc! Watching the clock spin is the highlight of my year!

[SidewaysSi]

I once showed a date my spinning dials and she was hugely impressed.

[Bobupndown]

It's for show.
Turned it on in several VWs using VCDS. It's called 'celebration' by VW.
I quite like it.

[Lotobear]

The first car I ever had that did this was a Subaru Legacy, I assumed it was just for theatre as others have suggested.

[alangla]

My 2006 Honda NT700 bike did this, but the wife's 2012 Jazz didn't, so it's not even consistent within manufacturers. On late 2000s Focuses, you could get them to do it, but it was a test function in a hidden menu in the dashboard not something it did as standard, the next function along made all the LEDs on the dash light up.

Overall, it seems a bit pointless doing it each time it starts & clearly some manufacturers don't find it necessary.