I presume that you all have electronic programable speedos from VDO as i do .
When i first picked up my car the speedo was very erratic , sometimes fast by as much as 20 kph and sometimes slow . Totaly random and no amount of resetting with the ign switch or the battery master made any difference .
I checked wiring connections and made sure i had a full 12 v and a good ground then recalbrated as per VDO instructions i found on the web ,all to no avail . I also noticed that the speedo head had been replaced twice for the same issue before i bought the car .
I concluded that i was getting a "dirty" signal from the speed sensor so i added a capacitor to the signal connection on the back of the instrument and recalibrated .
Now its deadly accurate and hasnt missbehaved in any way for the last 15 months and probably 5000kms .
The capacitor i used was just an old condenser from an old distriburor i had lying around , but one should be avaliable for very little money from any parts source and they are all the same essentialy .
Worth a try i would think for a couple of pounds and 10 min work ?
