massey

heres how the story goes, when you turn on the ignition there is no battery light, the display lights are really dim as are the head lights and heater if thats on, when you rev it over 4500rpm the altonator kicks in all lights get bright etc, ive changed the altonator to a brand new one check't the wires, is there anything else to check other wise im gonna break the car, its a saff cossie by the way, thanks for any advice

Wardy257

How did you check the wires? If it was anything other than by Volt Dropping you need to do it again.

massey

the voltage seems ok when its running, i traced the wires all the way back from the alterntor to the fuse box, i noticed there is the bat + 13mm bolt the other little wire and thats all mine has, no earth is this right?

iansoutham

Take the small blue wire and connect it to earth. Turn the ignition on and see if the battery light is on. If it is, then the alternator diode pack is dead or you have connected it to the "W" terminal instead of the "D+" one, if not, either you have a break in the wiring or the dash bulb has gone kaput.

If it was a fuse that was gone, you would have no handbrake light, oil pressure light or rev-counter.

The alternator earths through its mountings to the engine.

massey

the rev counter does keep playing up aswell, its deffo on the d+ mate i will check the earthing out the blue wire in the morning, were is the diode pack? it is a brand new alternator thanks for the info

iansoutham

The diode pack is built into the alternator itself. Just because it is a new alternator, doesn't mean it can't be faulty. Test the blue wire as you say, and let me know the outcome and I will assists where possible.

massey

ill test it 2moro. thx for your help

tabetha

Check for CORROSION INSIDE THE TERMINAL that fits on the warning light connector,
Connect a voltmetre to battery run the engine WITHOUT THE lgnition warning light wire connected, touch a LIVE onto the terminal on alternator on which warning light wire goes, it should now start charging, if it does not it is duff.
When you say there is no warning light(charge), this should give you a clue, if it was not working the alternator would not start the charging process at all ever as it needs a LIVE FEED THROUGH BULB ALL THE WAY DOWN BLUE WIRE to ENERGISE FILED WINDINGS IN ALTERNATOR, to initiate charge process, once charging process initiated it outputs POSITIVE at this terminal and light goes out as two positives do not make a bulb work(warning light).
The bulb for charge warning may just have gone black.
tabetha

massey

i earthed the blue wire and the warning light on the dash didn't light up, if i cut off the terminal and put a diffrent conecter on would this work? the wire were it goes into the conection feels like there aint nothing inside, the head lights are getting brighter at 4000rpm today to start the charging process

massey

tabatha the volt readings are 11.8 before i rev it up then like i say it shoots up to 13.8 and stayes about that

iansoutham

Right, point to note for everyone.

An alternator WILL self-start when speed increases sufficiently due to internal back-feed through the diode pack. This is normally around the 3k mark (depending on pulley size).

If you have put the blue wire to earth and nothing happened, changing the connector will make no difference. Next step is to take the dash clocks out and check / change the bulb. You will probably find that this is the issue.