Morris Minor Owners Club

How can I tell what size/output an alternator is and whether it is pos or neg? Early Minor alternators were pos I believe

Never heard of a +ve earth alternator. Minors were +ve earth with dynamos until very late on in manufacture.
Converted mine to -ve earth so that I could use an alternator.
John

Only VERY early 11 AC alternators were +ve earth. This was used with a 4TR box - and a 6RA relay. Any Lucas ACR alternator will be fine for you -and -ve earth of course.

From a box of assorted alternators how would I know what the output of any of the alternators was?

It doesn't matter - any of them will be fine for a Minor. Obviously an 18 ACR gives slightly more than a 16ACR or a 17 ACR....

But how can I identify a 16,17 or 18 ACR?

Should be a tag or a stamping - but honestly - ANY of them are plenty for a Minor. Just concentrate on getting a GOOD one, that works...

Mike,

As Roy says, there should be an aluminium tag with the ACR type on it, otherwise connect it up and if you have an ammeter see what output you can get from it.

The table below gives the rated output for all the Lucas ACR range, and also the main output cable sizes required for minimum volt drop at full output. The main output connections are 2 x 9.5mm Lucar, with a rated capacity of 35A, so any alternator with a >35A output should have 2 cables to share the load. Apart from the smallest one (15ACR) I would suggest fitting 2 cables to the rest of them.
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Crikey - I had never heard of the 20/23/25 ACRs !! I ran an 18 ACR in my Rally Elf and it handled headlamps and 4 X Cibies on stages ok !

4 Cibies? Wow, had just 2 Super Oscars and they cost more than the cars (MGA and Riley 1.5). Happy days!

Thank you for the info, I will file that and it may find its way into my Series MM and later cars handbook if that is OK