…and don’t forget the clock if you are converting to neg earth!
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Be careful if installing an alternator producing more amps than the wiring can handle. Fire hazard! An alternator rated higher than 45 amps should be wired directly to the battery.
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Another good point Bpp - a bit late for you, Jim, but Autosparks will build a harness with higher-rated cable if you ask. The Cobra with the Dynator in the photo above has cable that is good for 60A in the charging circuit.
As Eric says, the ammeter needs modification too - the Cobra has the same Lucas BM4 ammeter internals as the XK, so when I had mine rebuilt by Speedycables I asked Andy to modify it to 60-0-60A without changing the dial.
I think I would still like to see the charge/discharge indication on the ammeter which will be absent if the alternator output is wired directly to the battery. I suppose a voltmeter is an option but the wiring from the (now redundant) regulator to the ammeter and from the ammeter to the solenoid could either be replaced or doubled up which would solve the problem.
If following the standard wiring route, there will be a connector on the ignition switch and another one on the lighting switch before the two on the ammeter. I’m probably preaching to choir here, but it is important that connectors at these points are made off properly, soldered rather than crimped for preference. Poorly made connectors carrying even moderate currents get surprisingly hot quite quickly.
I did mention shunting the ammeter but it’s a bit borderline whether it’s necessary or not. They are pretty simple and robust. Are you really going to be charging or discharging at more than 30 amps for any length of time even though the alternator is capable of it? Most of the time the needle should be hovering around the zero. In my view, the main reason for preferring an alternator over a dynamo is for the higher output at low revs and the improved regulation.
I’d agree with Eric regarding the reasons for converting. The only high current drain on my old cars (apart from the starter motor, which is not in the ammeter circuit) is aftermarket electric fans. Dependent on the model used they can give quite a spike when they kick in, but probably not enough to tax a 30A ammeter.
Just saw this. I found out the hard way in 1980 on a very early Cobra!