second alternator install

timtheenchanteruk said:

ahh ballcocks....

im pretty sure you are correct sir...

Dammit...

hooked up a lil 3W rice lamp last night, and its not illuminating, I appear not to have 12V at the D+ when the engine is off either, which I beleive it should have, and I have a 1/4 amp discharge rate (250mA) looks like I'm shopping for a new diode pack grrrr.

Bizzarly once its running, its charging fine, voltage is ok, not measured the amps cos my ammeter only goes to 10.

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The lamp should go from 12 volts to the D+. There should not be 12 volts at D+ with the engine off, the armature coil is low resistance and provides the ground path for the lamp to illuminate it. D+ should rise to 12 volts with the engine running thus turning the lamp off.
The alternator will still charge, albeit with lots of electrical noise, with one duff diode in the diode pack but will drain the battery when not runing.
I used to rebuild alternators as a side line

can you not simplify the install by hanging a new lamp going to D+ on the new alt from the existing ign switch and running the battery wire from b+ to the second battery.

second batt just earths via chassis, alt via mounting bolts.

or does this cause issues?

trax said:

can you not simplify the install by hanging a new lamp going to D+ on the new alt from the existing ign switch and running the battery wire from b+ to the second battery.

second batt just earths via chassis, alt via mounting bolts.

or does this cause issues?

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Exactly how to do it

trax said:

can you not simplify the install by hanging a new lamp going to D+ on the new alt from the existing ign switch and running the battery wire from b+ to the second battery.

second batt just earths via chassis, alt via mounting bolts.

or does this cause issues?

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Done this (now) but not till after ive damaged the diodes (or strongly suspect I have)
Had a look, at least new diode packs for it is only tenner.

and my bad, yeah, of course theres no 12V at D+ with the engine off, duh....

whatever way I look at it, I did it wrong and broked it, and now I feel like a tit.

live and learn, i've done plenty worse than that before

so was the diag you showed slightly wrong or just youd wired it worng, ratehr check before i bugger something up lol

on my 2nd alt install we wired in a relay and charge light and an exciter wire without which nothing worked

Paulmitchell1984 said:

so was the diag you showed slightly wrong or just youd wired it worng, ratehr check before i bugger something up lol

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The diagram is fine, I ommited the lamp, figuring it was for a telltale rather than any functional purpose and I was going to fit a voltmeter for it anyway...
apparently it is

Good news is the diode pack (now confirmed as U/S) is only about a tenner

timtheenchanteruk said:

The diagram is fine, I ommited the lamp, figuring it was for a telltale rather than any functional purpose and I was going to fit a voltmeter for it anyway...
apparently it is

Good news is the diode pack (now confirmed as U/S) is only about a tenner

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Regulator may also be fubarred

regulator is fine, its not over/undervolting, its bang on 14.4V

timtheenchanteruk said:

regulator is fine, its not over/undervolting, its bang on 14.4V

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Good