Bit of help needed please

[stagg65]

Bought a new diesel rev counter today for my t25 1.9 diesel, plumbed it in and it sits at 5000 on tick over then goes off the clock when i rev it.
Do i need a pulse converter and if so where the hell do i get one from.

[ewenmaclean]

Hello,

what's the rev counter? If it's aftermarket, there's a switch on the back which sets the number of cylinders - obviously this should be 4, then there's a dial also to fine tune/calibrate it. I take it you're running it from the W pin?

Ewen

[stagg65]

Hello,

what's the rev counter? If it's aftermarket, there's a switch on the back which sets the number of cylinders - obviously this should be 4, then there's a dial also to fine tune/calibrate it. I take it you're running it from the W pin?

Ewen

Yes after market ive set it to 4 and tried turning it down but not enough.
Plus when i put heater or lights or anything that puts a drain on the battery the rev counter goes mad.
Even tries connecting wires direct to altornator

[ewenmaclean]

Are you sure it's wired up properly - all you should need is +12v from ignition, earth and source from the W pin off the alternator, which you can get from the multipin connector pin 9....

if that's how it is then I'm afraid I don't know, but someone else might well!

[stagg65]

Yes wired up to 9, got it off flea bay came from Dublin base company.
It even says diesel on the rev counter so im sure thats right.
By the way ive got two wires on the back of my alternator one red one blue-ish i take it the red one is the w wire.

[ewenmaclean]

Blue is the exciter wire - the W pin will be marked. If I'm not mistaken it's usually green, but I can't be sure...

[stagg65]

Sorry being a bit thick wots a exciter wire ?

[stagg65]

Im beginning to think the rev counter is faulty, when i turn my lights on the rev counter goes off the clock.

[billy739]

take the revocounter so it is next to the alternator!

red wire (+) on tach goes to red wire on alternator( biggest wire)


black tacho wire (-)goes to the metal of the alternator

do not use the small blue wire on alternator.

look on the rear of the alternator not in the same plug as above to wires. there should be a hole abnout the size of a termainal with a 'W' stamped nearby inthe aluminium.
in the hole is the terminal for the out put poss a brown or green wire (signal) on your tacho

[stagg65]

Yep tried all that sending it back and going to try and find an old golf tacho and redesign my one by losing the clock.

[ewenmaclean]

just to answer your other question...

the exciter wire is what provides altenator with +12v before it is charging, when the alternator acts as earth - when it starts charging it equalises this voltage using the internal diode - then there is no potential difference across the warning light terminals and it goes out.

The practical upshot of this is that it's a useful wire to use for circuits you want to be on only when the engine is running - e.g. charging the leisure battery. The blue wire provides +14v (ish) only when the warning light has gone out. I have coolant glow plugs for the winter for example, but they are on a switch and if I left it on they would quickly discharge the battery - hence I run them off a relay where the +12v source is fed from the exciter wire - the blue wire at the back of the alternator. Then it doesn't matter if I leave the switch on.

Hope that makes sense.

[stagg65]

Funnily enough it does and i am going to use the same wire for my relay when i fit my split charger for my leisure battery.
Many thanks for that.