Wireing and alternators...

I was poking around my alternator (the one I suspect of being duff) and after also looking at the wireing diagram came to the conclusion that it may be the wire to the battery (via the starter).

Q1 Would there be anything wrong in running an additional wire from the same output on the alternator to the battery?

Q2 how does the alternator warning light work? I see it's connected in parrallel with a resistor, would I be right in thinking that the warning light illuminates if there is a voltage difference between the alternator output and the battery? and this is why the warning light lights up before you start the engine? if this is the case, and my warning light is very dim(ignition on, engine off), then this points to the alternators connection to earth?

Q3 there are three outputs on my alternator, one goes to the battery, one to the warning light circuit and the other is not used (correctly according to the diagrams), however the third connector IS used on the V8 (according to the diagrams) and connects also to the battery, why is this?

If anyone more electrically minded can shed any light here I'd appreciate it.

PS, I now have reversing lights, a PAIR of stop/tail lights and a left rear indicator, hurrah!.

PPS, Muffin got's it's feet mucky on a rough little track I know of around 2-3 miles long yesterday, :o)

-- Regards. Mark.(AKA, Mr.Nice.) ___________________________________________________________ "To know the character of a man, give him anonymity" - Mr.Nice.

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Mr.Nice.
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The alternator light works by earthing through the alternator when not charging. When charging commences the light is no longer earthed and goes out. It's likely the diodes are shot in the alternator. Get a replacement from your local car breakers. It doesn't have to be from a LR as long as it's the same type and the mounting bracket is the same way round. There is nothing wrong with running the connection direct to the battery. The original only goes to the starter terminal for wiring convenience. The two large terminals on the back are linked and identical. Cheers, Peter

Reply to
Peter

Just something i learnet while reading every web page out ther on alternators before i fitted my twin alternator set up on my van,

there is actually a reason for the alternator output going to the starter terminal and not the battery direct appart from a shorter/one less cable, the feed to the interior of the vehicle/fusebox is most likely picked up from the starter terminal.. this is done so that when your headlights are on, the alternator sends it's power to the starter terminal, where the fusebox picks up the slightly higher voltage there before it gets to the battery, the result is slightly brighter headlights,

for brighter headlights put in relays at the bulbs, and feed the bulbs via the relays switch contacts from the output from the alternator/starter and not the battery, this just prevents the battery absorbing a few fractions of a volt.. or on bad voltage loss conditions with old long undersized wires, a few volts even.

the OP asked about the small connection to the battery on certian alternators, most alternators are 'machine sensed' nowadays, this means that the internal regulator picks up it's voltage referance from the alternator output terminal.. via an internal connection,

the other method is voltage sense, this type the regulators voltage referance is taken from the battery positive terminal, this has a few good points.. you'll always get a little voltage loss through the wires from the alt to the battery, so the voltage sense alternator will correct this by upping the actual voltage at the alts output terminal,

this is especialy usefull if you have split charge diodes in the circuit, these drop upto 0.4 to 0.7 of a volt through them, to a battery that's a lot.. lead acid car batteries need over 13.8 volts to charge properly, alternator puts out 14.4 volts (some less) you loose .4 to .7 of a volt in a diode.. and your effectively reducing the charge the battery can recieve, it will charge.. just never fully.. normal alternators dont charge more than 70 to 80% anyway.. complex reasons most people dont care about, unless your trying to charge leisure batteries in paralell, and want them to last longer.

anyway, if the diode in the circuit, or even a shunt measuring current was in the circuit, and you dropped .4 of a volt on the way to the battery, the voltage sense alternator will up the voltage at it's output terminal to 14.8 volts to ensure you get 14.4 volts at the battery terminals.

Reply to
CampinGazz

Twas Sat, 17 Jan 2004 18:31:07 -0000 when "Peter" put finger to keyboard producing:

I have a replacement on the way (though it's been a few days now and I've heard nothing, I'd better chase that up). Thanks.

-- Regards. Mark.(AKA, Mr.Nice.) ___________________________________________________________ "To know the character of a man, give him anonymity" - Mr.Nice.

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Mr.Nice.

Twas Sat, 17 Jan 2004 21:09:24 +0000 (UTC) when "CampinGazz" put finger to keyboard producing:

Alot of info there, and needed too as I intend installing more complex electrics later, thank you.

-- Regards. Mark.(AKA, Mr.Nice.) ___________________________________________________________ "To know the character of a man, give him anonymity" - Mr.Nice.

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