C5 speedo reading low

BaldEagle · Post by **BaldEagle** » 06 Apr 2009, 20:23

I have a 06 C5 Estate HDi VTR purchased in January. For some time I've noticed that I seem to trip those 30 mph flashing signs even when not going fast.

Last weekend I used the cruise control for the first time. With the cruise set at 70 the speedo indicated 60. Dropping it down to 60 gave an indicated 50. I then tried the speed limiter set to 30 - the speedo indicated 20. I have since been able to check with a satnav which confirms that the cruise is correct and the speedo reading is 7 to 10 mph under the true speed. Could explain why I recently got caught at 39 in a 30 limit!

Does anyone have any idea what may be causing this and if there is a fix? I'll probably take it to a dealer to sort, but would like to go forearmed with some knowledge.

Thanks

JC

wheeler · Post by **wheeler** » 06 Apr 2009, 23:10

It sounds like a configuration problem to me, possibly the wrong tyre size programed into the ABS ECU. Does it have the original wheels on it ?

bencowell · Post by **bencowell** » 08 Apr 2009, 20:16

Does the speedo needle obscure the mileage display when stationery?

My C5 needle had slipped before I bought it. They put a new set of clocks in under warranty. About £240+vat if I remember.

BaldEagle · Post by **BaldEagle** » 11 Apr 2009, 11:44

Thanks for reply - sorry to be so long getting back. Things have been unexpectedly hectic.

Firstly, the wheels are 16" citroen alloys with 215/55R16 tyres. I think this is the standard size.

Secondly, the needle doesn't fully obscure the mileage display but does sit just over the start of it. It is certainly below the first mark - presumably zero mph - on the dial so that before it even starts to register you are doing around 10mph. I've looked at our other and neighbours cars and the needles on them sit exactly on the zero. Would like to compare with another C5 just to confirm, but looks like you've cracked it!
Unfortunately mine is out of warranty so I'll stick a mark on the glass at 30 while I save up for the repair.

JC

dnsey · Post by **dnsey** » 11 Apr 2009, 13:14

I've not stripped a C5 instrument cluster, but I'm sure that it's not much different from others. They can be dismantled with care, and your speedo needle could be reset in the correct position. Just work methodically, in a clean environment, and don't force anything!