another speedo problem

[BERGS2]

similar to Oatz - the speedo on my S2 has developed a rather annoying fault.

Under 'normal' driving it functions perfectly well - however under heavy accelleration the reading drops by about half, floats around a bit & only returns to the true reading once you are off the gas again.

1) anyone know how to fix
2) will it fail its MOT for this quirk (you wouldnt notice it unless you boot the throttle)

cheers all,

Tim

[shnozz]

probably nothing to do with it but my speedo in the S used to bounce all over the place in 4th gear. Every other gear it was steady as a rock and then change into 4th and it would bounce between 20 and 80mph.

Previous owner tried all sorts to fix it with no joy. By coincidence, I needed the fuse box replacing when a coil wire burnt out. Low and behold, the speedo problem dissapeared when the fuse box was replaced. Dont ask me how, but might be worth looking around in that passenger footwell..

[kev s3]

speedo is not part of m.o.t. so wont be a problem,may be the sender unit.you can check for signal from the sender at pin 4 on your ecu.this can be difficult.checked mine by jacking up the back of the car and rotating the wheels..my sender had burnt out and the wiring insulation had come away where it goes into the sender. this caused a short. the speedo worked sometimes but not others. theres details in the bible about testing.
hope this helps cheers

[tvrgit]

my speedo jumped about all over the place till the ignition switch connector burnt out. When I fixed it, the problem disappeared.

The speedo obviously doesn't like weak or intermittent connections so check them all...

[steve b]

I wounder if your alternator is on the way out and the extra power draw during acceleration is taking power from the rest of the system.

.... just a thought .. it's definately something a bit obscure - do your lights or anything else dim on the same circuit as the speedo dim could be a dodgy power supply/connection.