C5 speedo

citronut · Post by **citronut** » 04 Oct 2010, 12:50

i have just had someone ask me what is the cause of his C5 speedo reading about 8 to 9 MPH under what its realy doing,

he has found by driveing through speed camera's at 30MPH they flash, but if he stays below 21MPH they dont,

i have not seen the car yet and dont know exactly what modle it is, i think he say its a 2.0lt diesel,

regards malcolm

Clogzz · Post by **Clogzz** » 04 Oct 2010, 13:04

The tyres may be too big.
Increasing the diameter by 1” increases the rolling circumference by 3” or something.

Post by **myglaren** » 04 Oct 2010, 13:09

Thought of that Cloggz but thought it unlikely to make such a difference

I find that mine, as with most, reads high (but note that some speed indicator signs read low and will flash up 30+ when you are only doing 28.

My guess - somewhat overshadowed by Cloggz info, would be the speed sensor - which is part of the ABS system.

Post by **Paul-R** » 04 Oct 2010, 13:49

Put it on a Lexia and check that the correct size tyres have been ebtered.

Citroenmad · Post by **Citroenmad** » 04 Oct 2010, 21:10

I find the C5s to be very accurate. Our C5 SX is spot on, when i had larger wheels on from a C5 estate it was underreading by mph what i was actually doing. If i was going by the speedo doing 70 id really be doing 72.

Apparanty C5s can be set by a lexia to tell them what size wheels they are wearing?

bencowell · Post by **bencowell** » 04 Oct 2010, 23:31

Has the needle slipped on the speedo?
Mine had done that before I bought it.
It was always 10mph under.
Ben

jimleshed · Post by **jimleshed** » 05 Oct 2010, 11:27

Surely if it was a sensor (ABS for example) that would mean that would be out by 2/3rds ish of the whole speed range...so at 60mph it would show 40 (and when showing 60 you'd be doing 90) I think you may realise that something is seriously wrong. The same would be true for the wrong size tyres - either actually wrong or entered wrong in setup.
I could be wrong though...Tyres would need to be approx half as big again as they should be (eg 24" fitted instead of 16").........

But, if its out by a consistant 9mph (and I guess the needle is not moving until you have a good bit of speed on?) its got to be something else.

Needle in the wrong place sounds good to me! or something more complex and confusing...

jimleshed · Post by **jimleshed** » 05 Oct 2010, 11:42

Another thought.
If its out by 2/3rds over the range rather than just consistently 9mph, could it be a conversion error between MPH and Km?
19MPH = 30KmH (ish)

Can this be set anywhere? I think the speedo has dual speeds marked, but is there a KMH/MPH setting that could alter needle position? (asking the various Guru's here...)

Actually, I am clutching at straws....we really need a bit more info!

bencowell · Post by **bencowell** » 05 Oct 2010, 18:33

The needle doesn't move if you swap between readouts as mph and kph are on the same scale.

jimleshed · Post by **jimleshed** » 05 Oct 2010, 21:03

I know it doesnt, as I said that the dial was dual speed marked.
But, it doesn't stop the electronics having a conversion factor somewhere, for some reason best known to the French.
We still need more info from Citronut, if possible....

citronut · Post by **citronut** » 06 Oct 2010, 07:58

sorry Jim
this guy was directed to me by someone elss, i dont have any contact details,

so untill he come's back to get me to do other wsork we discused, i cant give you anymore info on this,

regards malcolm

wright · Post by **wright** » 06 Oct 2010, 09:09

if the motor on the speedo needle has been replaced, the needle was probably put back on wrong, a lexia help to calibrate, in the actuator tests it will put the needle to 4 different speeds, and you can adjust the needle until its at the correct point during an actuator test, i have done this on a few c5s

micky707 · Post by **micky707** » 23 Aug 2013, 21:40

Hi all, I have just upgraded to a 56 plate C5 VTR, and after the xsara find it amazingly comfortable and am well chuffed. Bought it at Auction and it has 48000 miles on it. 2 things wrong, first thing was the boot lid opened everytime you blipped the fob, wd40 in the catch and job sorted. The speedo was under reading by 8 mph as checked with tom tom, i have taken the advice from this thread and popped off the cluster front and unclipped to get at the needle and moved it in line with the tacho at 0, job done, test driven and so far so good, i cant imagine what citroen would charge for something like this but only took 20 mins, tacked it with a minute amount of no nails so it doesnt slip down again. Thanks for all your advice as it would not have been something i would have attempted normally.

Micky

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