Afternoon all

I think I've finally sussed out this alternator and bulb wiring lark but would like to run it past you lot before setting myself on fire

I need a switch positive to the rear of the alternator and a switched positive to the warning light which then continues to the rear of the alternator.

Lastly a thick brown connected to the alternator to allow battery charging.

When the alternator is running I should get approx 14V at the battery terminals

And lastly the alternator draws approx 3.2A from the switch positive connection when running.

Have i got the facts right or have I got it completely wrong and talking out of the top of my head?

Many thanks, if i got it right I should have a fully running charging system tonight

Sounds about right.
The only way you can blow it up is if you connect an earth to the terminals so if you do it your way, it will either work or not. (not blow up!)

you don;t need a switched live to the alterator, and one through the llamp, just a switch live through the lamp, then onto the alternator

like this..

BAT+--------------IGN----------Lamp-------Alternator

you also need the large cable to allow charging to the battery, and a -ve on the alternator

hth

Ray

Oh confused now

I thought it worked like this

thin brown 12v in switch supply to excite coils
switch feed through light to alternator connection

When alternator starts to charge earth light earth on alternator has 12v at it so no flow of elec and bulb goes out

thick brown for elec to battery

would like to get this working tonight so all assistnace greatly appreciated

Thanks
Nigel

[Edited on 12/11/07 by jabbahutt]

a picurtre is worth 1000000 words.

notes.
1. alternator bodyt is the return to battery ie.e. 0V or earth (different names for same thing).

2. depending on alterantor type, the small terminal goes to the lamp; other end of lamp is switched to 12 V.

this supply field current current. when alternator is chaging, the voltage on both sides of the lamp is 12 V so it goes out.

3. big termianls, 2 of on a Lucas, are the ouput - they goe to positive of battery; this can be via a terminal on the solenoid.
Rescued attachment alt.jpg

thanks for that though your sketch throws up one last question

The small connection to the alternator before the switch, surely if before the switch and not after wouldn't that allow permenant supply to the alternator and therefore a flat battery if left connected?

That is how my original loom is anf I ended up with a flat battery hence my belieft that both the bulb connection and the other 12v were both switched?

Thanks for the help

I assume the alternator has diode (s) in that direct connection so it a) rectifies the alternator ac and b) allows current to pass from the alternator to the battery (for charging) but not from the battery to the alternator (for flat batterying )

The connections depend on what alternator you are using.
Old lucas alternators , the type with the big plug that has two big spades and one small spade, only need the big fat unswitched live to the battery positive and the switched through the ignition dash lamp live.
Many small japanese type alternators add an extra switched live to the above tally.
What alternator are you fitting?

it's off a Charade, two small spades on the rear and a large stud on the casing.

I know the thick brown wire for charging the battery connects to the large stud.

i know understand the wiring for the charge lamp to one of the small spades but when i attached the thin brown which is permenant live I ended up with a flat battery so I assume rightly or wrong that it must be a switched live instead.

The output from the alternator is not switched - alternators can output 120 A or more so you would need a pretty hefty swtich for that.

As ^^^ says, there are diodes in the alternator that prevent the battery discharging.

I am not an auto electricion so do not know every signle type of alternator but the above applies to Luvcas type (Magnetoi MAreli/Valeo and a fair number of others).

Charade alternator. Is that the one with the two connectors in a T shape. I will put a pic of the wiring in my archive as I still can't post in threads. You are right to say the two smaller connectors have connections that are only live when the ignition is on. One is direct from any ignition live circuit, one is from ignition live circuit through the ignition light on the dash and then to the alternator.

Cheers Dusty

Yep it's the one with the two spades in a T configuaration. Now I can get on with attempting to wire it up.

Many thanks