Battery not charging

[richs2000]

Hi

Newbie alert i'm afraid. I've got a 1.9l petrol T25 and the battery has stopped charging from the alternator.

Charges ok from the ZIG unit and starts the van ok when charged. After full charge and and cranking the engine it shows 12.8v which i think is ok.

When the engine is running (off the hook-up) the voltage stays stable at 12.6v, i would expect it to get up to 13.something.

I've jabbed the multimeter into the thin red wire that comes out the top of the back of alternator and get 15ish volts. There are 2 other thicker cables that head from the engine bay to the cab which i can't get a reading from (because i can't see where they go).

Interestingly, and i may be showing my complete lack of knowledge here but once the engine is running, if i take the + off the battery then the engine dies. i would have thought it would keep going, getting power from the alternator. I guess the battery forms part of the circuit?

Anyone got any ideas on what to do? I though it was voltage regulator after looking on here however can't see one on my Bosch 45amp alternator.

Cheers
Rich

[Aidan]

cable from alternator to starter motor has failed probably, that's how the connection to the battery is made - it should be a big fat copper ring, but often they get cut off and replaced with a spade terminal when some numpty does a solenoid rebuild and uses the wrong cap with the short threaded connection and then the fat one won't fit,
at a guess
get it looked at because you've potentially got that 15V live floating about

[richs2000]

is there a circuit diagram floating round that would help me find this ring?

I don't even know where the starter motor is...is it the in the belt loop of engine, alternator...?

also the thinner red cable that comes out the top of the back of alternator goes to a small relay type thing with a 10 (amp?) fuse in that is screwed to the side of the engine bay. about 5 wires go into it. is that the earth? don't think so but.....

rich

[kevtherev]

Bosch or not the brush pack is the same... and in the same place.
It's only a tenner so I would replace it, even if it has no effect a new one is always useful as a spare.
two 5mm screws hold the brushes in.
it's easier with the Alt removed.

there's a big 8mm thick terminal on the back of the Alt. (+ ve)
use that the test the output, with the chassis as earth.

it should read over 14V