Thread: tachometer works/doesnt work

Hi guys,
I had some probs with my tacho when I got my vehicle back from the mechanics about a month ago.Mechanic said it could be the alternator--he was right.

Anyway,changed alternator,everything was going along swimmingly,when I noticed that the tacho would drop down to zero,(when changing gear)then bounce back up to the revs that I was doing at the time.This would only happen every 3rd or 4th day,and only when I had started the car up that morning and was driving down the street.
Yesterday,I didnt have any tacho reading when going to/from work--Today,nothing on the way to work,but coming home from work tonight,it started out with no reading,but when I was 1/2 way home I noticed that it was working again..

Can anyone give me a clue as to what might be happening......Have already thought of pulling the instrument binacle out to see if its a loose connection behind the tacho....otherwise I dont have a clue...

Cheers
gazza
92 disco tdi

Now mine is a 300 Tdi experience (with deference to Andrew's advice) and in support of nzoliver.

I crimped a new connection onto the wire located on the back of the alternator that sends the signal to the tacho....problem solved. Loose connection both at the alternator and the connection with the wire. A combination of dirt, vibration and oxidised copper wire.