Hi i've got a 1998 hardy 24 with a volvo penta D41-L 150 HP fitted ,the faults with the tacho it's stopped working, its a VDO N 02 070 009 when the ignition is switched on the needle falls back from off scale to 0 when the engine is started the needle just goes all the way around the clock and stays there.I have had the alternator checked out and it,s working ok anyone any idea what the problem is thanks AL