speedo over reading.

[Bick]

Hi all hope someone can point me in the right direction.

I bought a Relay van mk2 06 plate with the 2l HDI engine at the beginning of this year but the speedo has always over read e.g. when it says its doing 30 its only doing 28mph. This is not a major problem but it gets worse the faster you go so when the speedo says you are doing 60 you are only doing 53mph. I noticed it when using my sat nav and when coming up to those sighs that tell you how fast you are going! I also suspect its being a bit erratic at times but not sure on this.

I did suspect the gearbox sender unit but my mate a Citroen says they tend to work or not, he suspects the speedo head.

The 2L HDI engine and gearbox are the same fitted to a lot of Citroen and Peugeot cars so thought one of you guys may be able to help?

Many thanks

Bick

[Chlorate]

That's about normal actually, most speedos over-read by about 10%. Or at least that's how it's been whenever I've checked car speedometers against satnavs. It would seem likely to me that changing the speedo head on the dashboard wouldn't fix it, you'd need to recalibrate etc and I don't know how that would be done.

Alex

[lurchy666]

my xantia is the other way, when it says 30 your doing 34, 40 is 43, 50 is 51 then 60 and 70 are spot on, mine just seems to dislike the slow speeds, (yes my tires/wheels are all correct size)

[Old-Guy]

The Construction and Use Regulations require that speedometers (the limits for tachographs are much tighter) are accurate to within -0% and +10% (5% for cars registered after about 2008 IIRC) plus 2.5mph. The requirement that speedos must never under-read means that they are manufactured to deliberately over-read regardless of which tyre size (of the available options) and how much tread there is.

My Xantia is pretty good - it over-reads very slightly at 30 and gets progressively more optimistic - when I last checked (fairly new front tyres) my sat-nav says an indicated 70 was actually 66-67.

[Mandrake]

Yep, speedo over reading of up to 10% is normal, mine reads 70 when I'm really doing 63 on new original size tyres. Nothing to worry about and nothing much you can do about it anyway. Besides, its helping you to avoid getting a speeding ticket!

[Taffyrhys]

You are the lucky one, as my xantia S1 speedo was under estimating. When the speedo was reading 60mph, i was doing 65mph on the sat nav so had to be extra careful with speed cameras or average speed camera on motorway road works.

Happy days and by luck alone didn't get a speeding ticket

[Bick]

Hi all and thank you for the replies.

I was aware of the 10% margin but to be honest i havent ever had a vehicle this for out, i could say its a citroen thing but ive had a few of them now over the last 20+ years and never had one this far out, 1 or 2 mph out at 30-50 getting to 5 mph out at above legal motorway speeds.

But from your replies it seems ive been very lucky

Looks like live with it and take no notice - sounds good to me lol

Anyway thanks again folks

[rory_perrett]

My Xantia speedo reads on average 7% over, although this is not consistant across the speed range. I think the "inaccuracy" or more the built in overread is probably from the sensor as when I changed instrument pods the overread stayed the same as far as I could tell.

Rory

[Bick]

My Xantia speedo reads on average 7% over, although this is not consistant across the speed range. I think the "inaccuracy" or more the built in overread is probably from the sensor as when I changed instrument pods the overread stayed the same as far as I could tell.

Rory

hi Rory that is interesting, mine is inacurate different ammounts though the rainge and some days im sure its worse than others but i dont use my satnav every day so cant check.

And you replaced the clocks you say and it made no difference?

[Jeff]

When I had to repair the speedo stepper motor I set the speed exactly by driving past one of those road side speed warning signs that tell you the speed and moving the hand etc, especially at 30mph. I'd rather the speedo was spot on rather than over reading and not knowing exactly how fast I was going past speed camera's.

[Northern_Mike]

The Berlingo is spot on at 30,50 and 70 at the moment, but it's only done a couple of thousand miles on new tyres. It was 3mph out throughout on the Tom-Tom on the knackered old boots it had before.

The V6 said it was doing 141 when it was doing 144!

[C5Alan]

not sure what I need to fix on mine but it is under reading by at least 10mph which is quite worrying I was running around at 30 i thought which after cruising behind the missus also at 30 I was reading 20 I never check the sat nav as they are normally out but it was reading 28. I think it may have started acting up after hitting a pothole should that be miss the only bit of flat road in the town

[qprdude]

Original wheels? Standard size for the car?

[C5Alan]

Original wheels? Standard size for the car?

It has orig wheels and been running 205 55 15 tyres for months before the problem started so doubt it has anything to do with wheels

[jimca007]

ive got a 2.0 hdi c5 and my solution to this was a little simpler, maybe too simple but it worked! took out the console housing the speedo, removed the screws holding on the face plate and moved the needle round slightly on the shaft so 0mph reads 0mph and pretty much every other speed ( according to my sat nav but not sure how accurate that is ! ) was pretty much spot on or within an acceptable margin of error