classic rev counter died

1992lse · May 4, 2009

morning, i have in my trust my friends 1991 classic 3.9 vogue S.E
i moved her this morning and noticed the rev counter has decided to play dead, i wondered if anyone kew of any common faults to check for to remedy this annoying fault.
cheers
simon

classic kev · May 5, 2009

Check alternator - might as well get it serviced really, new brushes, slip rings and voltage regulator. Then check all the connections and hopefully all will be well.

Beast o Bodmin · May 5, 2009

Ive been unning me rev counter off my coil.Can i run it off the alternator as ive no coil anymore?

classic kev · May 5, 2009

Beast o Bodmin said:
Ive been unning me rev counter off my coil.Can i run it off the alternator as ive no coil anymore?

Dunno, i suppose it is possible. Best peeps to ask would be either eightinavee, ramon.alban or irishrover. As far as I know the tacho signal on 3.9 comes from the alternator and efi trigger from coil or something like that?

Beast o Bodmin · May 5, 2009

Thanks kev.Ive popped a post in general.

DC_ · May 5, 2009

I've been having a few probs recently with my 3.9
Alt, battery connections etc.
My old alt went dead and the nice men from the AA fitted a new one. Now i think the new one is a 200tdi one with the lucas plug terminals on the rear. They had to connect the wire for the rev counter up to the rear of the alt to get the rev counter working.

Tried it yesterday on the coil with no joy, so it seems fine for now on the back of the alt.

1992lse · May 6, 2009

well i fitted new alternator. and still no rev counter.wished i still had old speedo pod to see if its the rev counter itself. trust me to sell too much stuff on ebay.
suppose it's check for dodgy wire time. oh deep joy.
thanks gentlemen.
regards
Simon

classic kev · May 6, 2009

A bit strange that one. My rev counter dies when I take the Rangie swimming but once it's out of the water it comes back to life. I wouldn't have thought there is much to go astray because as far as I'm aware there is only one wire input from alternator to tacho. I suppose there could be a corroded plug/connector somewhere in there or as you say, maybe a duff tacho.

1992lse · May 7, 2009

decided to drink excessive amounts of booze yesterday, so i will have a look today, once my head stops spinning.
see if i can see a wiring fault. might just run a wire from alternator, to tacho, if it works then its been re-wired.

The Mad Hat Man · May 7, 2009

if it is a 3.9, then the chances are that the tacho is not driven by the alternator - more to the point, if you connect the tacho input to unkown outputs, particularly the alternator, then you stand a good chance of frying the tacho and possibly most of the electronics and engine wiring. If you dont know what you are doing, get a qualified sparks to do it - its cheaper, safer and saves the embarassment of explaining to yo mate why the engne bay has gone up in smoke.

Petrol engines run from the coil (they pick up firing pulses). Doozils dont have a coil, so they have a SPECIAL alternator that outputs pulses every revolution. This, of course will vary on relative pulley sizes - crank pulley to alt pulley.

DO NOT CONNECT TO THE ALTERNATOR!!!

BoB - i doubt it - because the tacho may well work in a different way.

classic kev · May 7, 2009

The Mad Hat Man said:
if it is a 3.9, then the chances are that the tacho is not driven by the alternator - more to the point, if you connect the tacho input to unkown outputs, particularly the alternator, then you stand a good chance of frying the tacho and possibly most of the electronics and engine wiring. If you dont know what you are doing, get a qualified sparks to do it - its cheaper, safer and saves the embarassment of explaining to yo mate why the engne bay has gone up in smoke.

Petrol engines run from the coil (they pick up firing pulses). Doozils dont have a coil, so they have a SPECIAL alternator that outputs pulses every revolution. This, of course will vary on relative pulley sizes - crank pulley to alt pulley.

DO NOT CONNECT TO THE ALTERNATOR!!!

BoB - i doubt it - because the tacho may well work in a different way.

You could be right but the wiring diagram suggests tacho input from alternator - white wire with silver stripe and an insulated spade terminal. The coil signal goes to ECU (to fire injection pulse?) white wire with black stripe, comes off coil negative.

Or at least that's what I understand.

1992lse · May 7, 2009

i tried a different tacho, and no joy, so its a wire problem. might get the sparky round to give his opinion. other than that i could buy a P38 and have all the nightmares you guys seem to have with them. no wonder i love my LSE.
thank you for all the help though gentlemen, been very helpful.
regards
Simon

classic rev counter died

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