Alternator trouble. Calling all electrical gurus!!


New Member
Ive posted this on the modifiers club too.

I really need some expertise here.

My alternator wasnt charging so I bought a new(used) one. Changed it but same thing happened: not charging. I bought a new battery too. Got another new(used) one and same thing.

I have tha battery in the boot so the main live wire goes from the alternator in to the connector by the wing then out to a connection box that goes to the battery and the starter I think. There is a circuit the whole way from the alternator terminal to the connection box and battery. The minus lead is okay and there is a circuit from the minus output on the alt. to the connection on the chassit.The main connector on the front has 12v.

When I disconnect the live and minus to the alternator it puts out 13.2 volts. When I connect it again and check the battery it doesnt charge and the volts steadily drop.

Does anyone know EXACTLY how the charging system works? Ive checked all fuses etc. All seems fine.

Where is the voltage regulator? Is it built into the alternator? I believe so myself. Does it regulate the live or the negative?

I hope someone out there that has a clue can be bothered answering. Im gettin really,really pissed off now.



New Member
Have you checked your getting a good earth, I had a similar issue which turned out to be an earthing issue. Connect a multi meter up to the chassis and insure the car isnt live and its earthing correctly.


Staff member
I'm pretty sure the voltage output should be 14.4 from the alternator; 13.8 sounds like a battery with no load on it (dropping to 12V with load). - As suggested on the other site, try re-earthing it to the block/body.


New Member
Do you have continuity between the altrernator heavy gauge wire and battery ? Get a heavy gauge wire and temporary fix it between the alternator postive and battery postive. Do the same with the negative too. Negative on the alternator is on the side (manifold side) of the alternator.

Report back


New Member
I'm pretty sure the voltage output should be 14.4 from the alternator; 13.8 sounds like a battery with no load on it (dropping to 12V with load). - As suggested on the other site, try re-earthing it to the block/body.
As per manual Regulated voltage output is 14.1-14.7. I am assuming this is with no load. Once load is applied voltage will drop.

I checked my Datascan logs and i have a constant voltage (reading from ecu) of 13.5v when idling, and goes down to 13.1v at high rpm. It could be mine is going nuts soon though.


New Member
Ive cleaned up the earth connections now. I had an amperemeter on the live cable and its charging ca 11-13amps. The volts werent dropping as quickly now but they were still going down slowly.

The battery lights not coming on at all. However when I switch the lights on the yellow light in the middle of the dash comes on and the car starts going lumpy. When I switch them off it goes fine again. I even put a jump lead on the negative pole on the alternator direct to the chassie but it didnt help.

Im gonna put a cable from the alternator directly to the battery just to see in case its been a combination of things thats caused this.

Im wondering if the batterys goosed now and not taking a charge. They do only take so many drains and re-charges. Its only a few months old but its been drained umpteen times now. Ill try with another battery too.

Anyone else??


New Member
Ive found the problem...almost

The wire that feeds the alternator with 12v to kick start it has 12v with the ignition off and then disappears when the ignition is on!! Does anyone know which relay it is? Ive temporarily fixed this by nicking 12v from elsewhere.

I had to use another battery and I can now see its charging. 13amp on tickover, up to 25a with the lights on and then 35a with the hazards and wipers on. Im giving the battery a charge overnight to see if thats okay. It seems the light at the end of the tunnel is getting closer.


Ive had issues with the 2 feed wires out to the Battery it was only charging 12.6
but anyways Glad you found the issue