Strange speedometer malfunction

[earthian]

Hi Guys,

At the moment I am on a phone with my mechanic, he is claiming that all parts are OK (-ish), but speedometer does not work anyway:

The sensor does provide signal (~6-8 Volts?) then the signal comes to the magic black in the dash and reaches the speedometer. However the voltage drops quite a lot at the speedometer to nearly 1V only. Could this be a fault in that magic black box which gives signal to ECU or maybe something wrong with ECU too?

Does anybody have any idea what could be wrong here?

Regards
Andy

[Tyre Tread]

Almost certainly the speedo head.

I just has the same problem. My speedo is currently at Speedy Cables.

Be warned, they are not so speedy. They're quoting 20 working days turnaround

[earthian]

Hi,

Thank you for the info... I have this feeling that i will have to replace the whole speedo system... The head (speedometer gauge + odometer) does seem to work when tested. Apparently the voltage drops before it reaches the head...

Regards
Andy

[Tyre Tread]

The voltage should drop.

What the intermediate box does is calculate the pulses. It the fowards a signal (Yellow or yellow and blue wire) to the speedo head. Steve Heath said it measure it better on a meter on an AC setting a its a pulse.

If you've got a signal feed as far as the head then its the speedo head itself.

Speedy cable repair for £55 or so.