I have a E reg Ford Cargo 813. A kindly person used a 24 volt supply to jump start the 12volt system recently. Now the speedo on the tacho and rev counter do not work.
When it was 'jumped' the tacho had a full scale deflection then the needle stuck in max position. It returned to zero when the head opened but now it does not move when the vehicle moves.
I assume it a fuse? Can anyone tell me where the fuse is situated? Thanks

Dave, November 2009

Its easy 1. turn key on tacho, pull down spedo door, remove any tacho paper. 2. On back of spedo door at the top is a small flap lift very gently until it stops, whilst its lifted you will see in side the housing of the tacho 3 tracer pins push in gently the bottom two the third one will then move down, let it come all the way down until it stops by its self. 3. take fingers off pins release flap, replace any tacho paper close door and turn key. You have now reset tacho and it wiil work properly. You must have a charged battery connected to do this, if you jump start or connect new batterys you may have to re-set again.

Bazzer, October 2010

Dave,
Did you have any joy ? I have just had the same thing occur under almost identical circumstances wih my Renault Magnum. It is a disc type tacho (as is yours I assume) and I am inclined to think it is an electrical thing rather that cable snapping. Maybe a reset.
So was wondering how you fixed yours !

Ron, December 2009

Tachographs are either mechanical or digital. Unlikely that you have a digital tachograph. A mechanical one (i.e. all the old ones) is driven by a flexible drive cable from an adaptor on the rear of the gearbox. Jump starting and 24 V won't have any effect on that. However if the drive cable snaps due to fatigue (which can easily happen) then the tachograph will read zero and the odometer ("mile-ometer") won't change. You need to get a new drive cable - easily done - they can usually use the original sheath and end fittings and just make up a new cable for you).
Which needle are you referring to? The stylus that marks the chart or the speedometer needle indicating your road speed?
There is a fuse for the speedometer/tachograph (fuse no. 15 - 10 Amp - if you have a 3 piece instrument panel). The fuse box is on the passenger side under the glove compartment. It is covered by a black plastic cover which is held in place by 2 plastic screws/buttons.

JD, November 2009