The only wires in the factory loom to worry about are the brown ones from the alternator's +12V output to the battery cable stud on the solenoid.

Early cars with the 15AC alternator (here in Oz) had 1 brown wire, later cars had 2. You would want 2 wires or a (4mm2 or bigger one) there, if going higher than 35A output.

for your car, I suggest an alternator that retains the look of the original generator.  A few companies make them, search "dynamo styled alternator".

Exactly! Full marks, John.

"Letting the smoke out" is doing something that overheats wires or components to the point something burns. In MK 1 Minis, it was pretty easy - they had only two 35A fuses to which were connected many small wires that might carry 10 amps. If one shorted, it was unlikely to blow the fuse, the wire could heat up red hot in seconds, melt its insulation away and that of anything in the same bundle. Lots of smoke gets out.

When we upgrade our alternators, we need to consider if the wire carrying that 70 amp current back to the fusebox or battery post of the solenoid is capable of carrying that load. I wonder what wire size can do that, and if the stock loom wire is big enough.

I think what Dan was asking is something to the effect of 'can the existing wiring loom handle the increased current'. 

How much current can the charging system handle?  What wire-size have we got and how much can it take before it melts/burns? 

The largest factory fitted alternators were only 70A.

I haven't had an issue with mine and I have been using it for the past three years now with positive results just as yourself.  I really just wanted the extra headroom of power in case I wanted to add extra goodies in the future.

Please school me on what this smoke thing is?  Im not savvy with electronics and I have never heard this term before.  Thanks!

The primary concern is what type of smoke it woud introduce to the electricals. Must be compatible with Lucas smoke or it will cause problems. Also too big an alternator may introduce too much smoke, causing it to leak out and escape. You never want to let the smoke out.

That's the same one I just replaced the old 35 with and I'm much happier.  Cranks longer, the headlights and 55W Oscars are searchlights.

I'm not aware of a reason not to go to a bigger alternator, perhaps there is and I just don't know.

I'm been using the 45A alternator for 16 years now - it was the first component I installed and it's been flawless.  Fog lamps, driving lamps, radio, cigar lighter, wide-band and all sorts of things are installed; never had a problem.  I installed an Optima Yellow Top (YT-R-2-7) battery in February 2014 only to make room for the spare tire after I'd installed the larger 9 gallon fuel tank.  The old Exide battery stays on the Ctek conditioner/charger and used to power the external exhaust sniffer and the hand-held H3 spotlamp/work lamp.

Speaking of massages in the far east, the best haircut I've ever gotten was in the barbershop at Camp Zama in Japan; she was around 80 years old and gave me such a vigorous head/neck/shoulder massage that seemingly never ended so after what seemed an eternity I started laughing from pain and begged her to stop.

All those "type" of purchases and stories from overseas stayed overseas.

that's the advantage of travelling, you get to experience the best of "both" worlds...  lol.

sir Dan you're question is so  naughty, revealing and very titillating...  come on be nice,  lol

Questions to Armycook:

.....so.... did you buy the camera? and did you get the full discount?

You remind me of this sales person in HongKong when I was in the Navy. He will say anything and I mean anything just to make a sale. And I mean the most bogus outrageous statements lol. Even told me he'd give me a 50% discount card to get a soapy massage with happy ending at Wan Chai and Tsim Tsa Tsui if I bought the damn camera. Haha!

Thanks guys.  Car is a 64 MK I Cooper with a 1293cc motor.  I am only running 4 Lucas 700's, a roof mount spotlight and about 8 red dash pealights.  Nothing else is wired in, no stereo, no lighter, nothing else...no wipers. As I said the generator has always been able to keep up.  Comments??

I ended up getting a much larger one for my mini as a just in case factor.  Here is the one I bought and I have had it for three years now with no problem //m.ebay.com/itm/Mini-Cooper-Classic-Alternator-Generator-95Amp-Drop-In-NEW-/251588475661

dude , you will obltain 34amps at 3k rpm.,it means you need to drive at least 50mph before you can even hear a sound from your radio, or light your cigarette,, remember that  the original classic minis with 850cc and original 34amps alternators were made for district nurses, to go just to and from the hospital. no radios, no cigarette lighter, no nothing, just an ashtray.

here's my advice 2u, if i were you i'd get the 65 amps for sale by our host.,  im telling you , you'll be happy with it, no more rattling of engine when you turn on the headlights and other accessories all at the same time.   its power when you need it.  it'll give you about 65 rock solid amps at

the 34amps alternator? hmm yah it's good too,  i use it to charge my AA batteries.   

I=P/V... ie the Amps (I) that your alternator needs to equal the demand , ie power (P) of all electrically driven devices divided by the system Voltage (V) (=12).  So add up all the loads than could possibly occurr... lights + stereo + heater + wipers + a bit for ignition + a bit to charge battery + maybe fuel pump +........ then divide by 12 to get the theoretical max alternator output you might require.  

In my case I have a total of 400 watts of lighting with everything burning.... this requires a alt output of (400/12 =) 33+ amps just for the lights.  So I just fitted a 50+ amp alternator from my local autoelec shop..  and much cheaper than a "Mini" alternator..  So far this has proved to be adequate (as Rolls Royce would say .

You don't need more than you can use - but enough reserve to allow for those long- dark - wet - cold - (boring?) trips is worth it.

Maybe some of the more electrically literate members can supply some numbers for typical ignition/heater fan/ charge etc useage??

Cheers, Ian

As Kevin said, if you are not running high-current accessories you will not need a bigger alternator, the 34 Aamp unit will be fine.  What you should notice is that your car will benefit from better charging at low engine speed.

Unless you run a big doof-doof stereo, either size works just fine. I use an old 34A (16ACR) one, it's been fine for the last 20+ years.

I am finally going to change out my generator for an alternator.  My generator kept up pretty well with the lights in the front as long as I ran the car for a few minutes when I got home.  Our host sells two size alternators...a 34 amp and a 45 amp will I notice a difference from the generator and the other size alternator and how much??