Speedo Diagnostics...

[Andrew Willcox]

So my speedo started to fail intermittently and now seems to have stopped working completely.  I also notice to he odometer is also not increasing.  Rev counter is also bouncing but i suspect this is unrelated - but will check the earth connections.

I did fit a new speedo drive unit a couple of years ago so I wouldn't expect that to have failed again so soon?

was thinking about fitting the sensor to an electric drill to see if that provides an out put that would drive the speedo - which might point to the worm gear being the issue.

Any other suggestions on how I can diagnose the fault?

Car is 2005 K Series with the Ford 5spd box

[Jonathan Kay]

Presumably mechanical off the gearbox?

... was thinking about fitting the sensor to an electric drill to see if that provides an out put that would drive the speedo

Yes, you can test cable to instrument that way,

I did fit a new speedo drive unit a couple of years ago so I wouldn't expect that to have failed again so soon?

I wouldn't assume that! Definitely have a good look and play with the angle drive. And check that the cable run doesn't have any kinks etc.

I'd also check the connection of the cable to the instrument.

If it is the instrument they are surprisingly repairable.

Jonathan

[Andrew Willcox]

Jonathan,

Speedo is electric, wires from the speed sensor on the gearbox to the speedo gauge.

Are the gauges serviceable at home or do they need to go to specialist?

Andrew

[Jonathan Kay]

Glad I asked!

The rev counter problem then could be related. All other instruments working OK? Any recent work?

Do you have a multimeter and the appropriate wiring diagram? Let me know if you need the latter.

The drill trick should work once you've got the sender unit out. NB ignition on.

Servicing the inside of an instrument would be well beyond me if it was anything but a disconnection. Might be something like £70 for an inspection and simple fix.

Jonathan

PS: Burton Power used to have an improved sender but I can't remember if that was mechanical or electrical.

[Geoff Brown]

I would suspect the gear box speed sensor. Mean time to failure on this sort of thing cannot be judged even if changed 'recently'.

You will probably find that the disturbance with the rev counter is a result of the failure of the sensor.

It is even worse with later cars where all the gauges are integrated as far as indication & power source is concerned. The failure of the hall effect sensor can cause all sorts of  mayhem.

[SLR No.77]

Andrew, if your gearbox sender is the type that screws to the side of the gearbox with a quill connection, just spinning the quill between your fingers will be enough to activate the speedo needle.

Stu.