Hi folks , Sometimes (usually when cold) my speedo doesnt work and will then just kick in and work as normal , other times I will be driving down the motorway and it will flick up to 120mph (without me doing 120mph) and then read as normal again . Any ideas ? I did try to do a quick search but didnt see anthing .

Dry joint on the back of the circuit board.

Get ready to change your clocks, mine did exactly the same , slowly got worse over x months , then died altogether, Also bear in mind your auto box change signal come from the clocks , so if they are not working correctly then its liable your auto box will do strange stuff as well.

this is a old post from Jeff tt

A lot of owners have issue with the speedo, power steering, auto box change etc.

All of these are related in as far as they are part of the speed sensor circuit, having seen many owners pondering on if the speed sensor is at fault then take a look at the picture below.

 

The speed sensor is rare in as far as it can be seen to be faulty by just looking at it provided of course you know what to look for.

 

The photo actually shows autobox sensors but the manual box sensor has the same issues.

 

The unit is a small pulse generator, as the cog is turned by the gearbox the stator is turned within the field windings which produces a small ac voltage of around 1 to 5 volts and as the unit is very unstressed there is very little that can go wrong with it.

 

However the unit is held together by the black plastic end cap, this end cap is where it all goes wrong, for reasons unknown the caps start to come adrift as seen in the photo.

 

This loosening of the end cap allows the stator shaft / field windings to move out of line not by much but enough to stop the output been produced.

 

Annoyingly as the cap originally starts to slowly moves out, the shaft end float is still small enough for it to move in and out of the correct position and so causes it to work intermittently.

 

So armed with this information all you need to do if faced with this problem is get the car jacked up and take a look at the end cap on the sensor, if it looks like the faulty one in the picture simply apply a layer of epoxy resin to the edge of the cap and push it back in, yes that simple, no need to even remove it, and you will have one fixed sensor for a tube of glue.

A Lexx said, most likely a dry joint on the speedo board, very common, also do you have a MPH convertor?

Yep resolder everything ,both sides