> Am having the weirdest problem with an 02 Ford Focus 1.6L Zetec - at
> random times and random speeds the speedo starts jumping up and down
> for a couple of seconds to a couple of minutes and in fact does not
> stop until the car's engine has been switched off or is idling,
> Has anyone out there experienced a similar problem with a Ford or have
> any idea what may be causing it. Investigations by my local garage
> confirm that this is not an electrical issue.
The speed signal is electrically generated from the VSS (Vehicle Speed
Sensor) mounted on the transmission. This is fed to the ECU. The ECU sends
an electrical signal to the speedometer.
I would be interested to know by what logic your local garage arrived at the
conclusion that it is not electrical...
Does the car run fault-free otherwise? If it has a mis-fire, suspect a coil
pack fault causing interference.
When the speedo is playing up does the milometer show "----"? If so, check
the wiring to the VSS, especially the connector on the top of it. If you
have to change the VSS just to eliminate it, the cost is about 25UKP and a
bit of a fiddly job to do yourself, or about 100UKP for a dealer to do.
(Google in this group for VSS - you will find plenty of info!)
Post back and let us know how you get on.
Remove prejudice to reply.