jumpy tacho

[tassydisco]

Hey all.
My 96 300tdi disco has a good old jumpy tacho. Bounces between 1000 and 3000rpm. As soon as I switch on the headlights its back to normal. Any ideas where I should start looking? Any advice is much appreciated.
Thanks - adam

[kreecha]

Hi Adam,
When mine played up at Cape York, I just cut the female spade connector off of the end of the tacho pickup wire on the back of the alternator, and I crimped a little section of new wire on (about 40mm) and a new female spade connector.

Problem fixed, so that is one place you could start.

Cheers, Adam.

[Fausto79]

HI Adam,

my tacho recently went dead and turned out that my alternator was about to have it. before that it was very smooth. it started off with big jumps and then it would sit on 0 until you reached over 2000rpm and it would kick into life. then all of a sudden completely kaput.

I have recently put a new alternator in and although the tacho is alive again it is a bit jumpy. especially in the higher rev range when im at highway speeds.

I assume this is a wiring problem and possible that the spade connector may need an exchange.

Do you know the history of your alternator? how much does it jump?

if you think your alternator is ok id say do what the other adam said. i think i might try his advice too and see if it fixes it. since the new alternator its only small jumps but still annoying.

[Blknight.aus]

start at the connector, then split the loom and inspect the wire itself finally put a decent meter on the output and see if its giving a good pulse count and check the output from the alternator to see if your getting bad diode ripple (it will show up as AC voltage or a DC frequency)

[tassydisco]

Thanks people. It was just the connection at the back of the alternator. Cut off the old one and replaced it and its all good. Thanks for your help. The alternator is only a year old so I was hoping it wasn't that! Cheers
Adam

[willedw]

thanks Tassie disco fixed my problem too

[loanrangie]

Unless the wire is weak/ broken usually you can just use pliers to close the spade connector a little to tighten its grip.

[DiscoMick]

Mine is jumpy too. The alternator was rebuilt last year so it should be good so I'm guessing a connection or cracked wire. Time for a fiddle...