I know it's been asked 1000 times and I have read through many of the discussions already but as I am ABSOLUTELY hopeless with electronics, can someone just set me straight:

I am going from Bosch alternator conversion back to Lucas Alternator. The Bosch has 3 cables, 1 big one which goes to solenoid but I have two smaller ones and both go to the fused ign switch of my fuse box. (The one that only has power when the ign key is switched on). Not sure why there's two but that's beside the point.

Is this how the Lucas 16/17ACR works? as in the bottom right diagram below?



Basically if I connect only one of those cables from the Lucas alternator to the switched fuse box, isn't that the same as the bottom right diagram?

Ping ConvertibleMini

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Lillee - 1969 Morris Mini K

Yes.

Internal regulator so one wire to battery, one to alternator and the other to the ign. light.

Thanks for the straight answer Steve. I might even have her running sooner than I thought with this out of the way

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Lillee - 1969 Morris Mini K

The positive cable from the alternator should go to the battery via the solenoid?

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67 Deluxe
Dry suspension
1293cc, 11:1 comp, RE 282 camshaft, 45 Weber, extractors etc
4 synchro close ratio gbox
Cooper S brakes, no booster
Stealth box, as Doc says "goes harder and idles!"
RH tank cos I needed it crossing the Nullarbor etc..

Yes, the +ve from the alternator should go to the battery, in this case the battery cable to the starter solenoid. The other is your ign. light, brown/yellow I think is the colour.

Although Minis were never built with any Electrical protection against reverse polarity it is advisable to install a fusible link on the Positive cable that feeds from the Battery side of the solenoid to the Alternator B+ terminal. Always closest to power source. It is much cheaper to replace a Fusible Link then replacing smoked out wires in the event of a battery mistakenly connected back to front.

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DID I MENTION THAT I AM THE BEST SUPPLIER FOR MINI ELECTRICAL PARTS AND REPAIRS?
"Let us remove your "SHORTS"

What specification of fuse?

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Lillee - 1969 Morris Mini K

With respect to the two small wires.

One is the alternator field supply and the other is the voltage sense. Field supply is the current which creates the rotating magnetic field which makes the big current flow. Voltage sense brings a measurement of the car's battery voltage to the alternator to tell it how hard it needs to work.

Sure both wires can do the same job of supplying 12 volts to the back of the alternator, but the voltage sense is supposed to test for exact battery voltage at the battery. The voltage sense wire should go to the solenoid for this reason.

It does this because testing the voltage at the other spots is not accurate. Resistances in the copper wire at high current show a higher voltage at the back of the alternator, and lower voltages at the fuses. Only small differences, but battery condition is based on decimal point differences in voltage.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Yes, but the Lucas does not have a voltage sense so the wire is now redundant. Just a big one to the solenoid/battery, the other to the ign. light.

As I have explained to Chong for the last 2 days. Somehow the wiring got butchered when the bosch alternator got fitted years ago. He needs to trace wiring from the light.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Yes, its tied to old technology. I believe it was a hangover from very early alternators setups. Modern regulators test for battery voltage much more intelligently. I have seen battery regulators stopping charging for a moment to test battery voltage before resuming charge.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Thanks guys. So if it blows up I can blame all of you right???

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Lillee - 1969 Morris Mini K

You know Ausmini. Our "Bullet Proof"* warranty extends to five minutes or the first start.











*Not actually bullet proof.

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

Yes I'm sure he is only joking.