16 replies to this topic

[woodsy483]

Just got round to putting all the wiring back on the starter, alternator, etc which I had all labeled up with idents.

Problem is though I have fitted a new 70amp alternator that has an earth stud but I cannot find a wire suitable with a ring tongue on that looks like an earth, should there be one or is it not needed.

[dklawson]

The case of the alternator should be at earth potential which means clean mounting bracket surfaces should suffice. However, since the maker provided your alternator with an earth stud it sure sounds like it would be nice to add am earth wire. Your original Lucas unit probably never had one.

[icklemini]

you *sure* its an earth stud? - never seen an alternator with one.....

[lrostoke]

Yes as above, some of the 70amp alternators have an additional 6mm stud which is 12volt live.

[MRA]

Alternators usually earth through their body, why is yours different ? how many studs has yours got ? and what make is it ??

[woodsy483]

Its a Lucas A127 70 amp similar to this one

http://cgi.ebay.co.u...=item2ea94ac504

It is normally fitted to mk4 escorts such as XR3i, it actually has 2 studs on it, I know if you search for a Lucas A127 on Ebay it comes up with a similar version for marine applications so maybe the studs are there for this purpose. Just for information the connector is exactly the same as the standard mini 3 terminal connector.

[lrostoke]

I'm running same alternator. No need for a seperate earth lead.

On mine there is the standard 3 pin (2 big, 1 small) connector. But also an additional 6mm stud connector which is optional to use.

[woodsy483]

Yes as above, some of the 70amp alternators have an additional 6mm stud which is 12volt live.

I'm running same alternator. No need for a seperate earth lead.

On mine there is the standard 3 pin (2 big, 1 small) connector. But also an additional 6mm stud connector which is optional to use.

So is this stud definately a 12v live supply

[Brams96]

Looking at the 2nd pic down the stud on the right has an insulated washer on the terminal so would not be an earth stud. Dont connect it to earth!

[lrostoke]

you'd have to stick a tester on it to be sure. But I know on mine I have a 3 pin socket and a 12v stud, I actually use the 12v stud for an additional cable.
Figured if uprating alternator may as well stick an additional charge wire in considering 1984 wiring wasn't made for a 70amp alternator.

[woodsy483]

Looking at the 2nd pic down the stud on the right has an insulated washer on the terminal so would not be an earth stud. Dont connect it to earth!

No I'm going to leave it as Irostoke said as it may be a 12v supply, if I have charging probs later I know where to look

[dklawson]

As I said in my first post, the mounting brackets should provide a good enough earth connection if they are clean. However, now that you have posted a link with pictures of the alternator, draw your attention to the second picture down as others referenced above.

The threaded stud to the right (at the 3:00 o'clock position) clearly has insulators on it. That WILL be a +12V output.

Still looking at the second picture down, look at the stud at the 12:00 o'clock position. That one (as far as I can tell from the pictures) does NOT appear to have any insulators. (You can also "sort-of" see this stud in the top picture... at the top). If the stud at 12:00 is in direct (metal to metal) contact with the housing, it IS an earth stud. As before, its use will be optional.

EDIT: Strikeout last paragraph as incorrect.

[icklemini]

As per AC's handy diagram:



The M6 output lug can be used to connect a heavy guage cable from the solenoid + to the alternator... provides a better connection than the plug.. (or use both!)

Edited by icklemini, 07 June 2011 - 01:33 PM.

[dklawson]

I stand corrected and will edit my last post.

The eBay link does specify that the M5 stud is "W" which would mean "phase" and agree with AD Dodds picture above.

Thanks for catching that!

[woodsy483]

As per AC's handy diagram:



The M6 output lug can be used to connect a heavy guage cable from the solenoid + to the alternator... provides a better connection than the plug.. (or use both!)

I stand corrected and will edit my last post.

The eBay link does specify that the M5 stud is "W" which would mean "phase" and agree with AD Dodds picture above.

Thanks for catching that!

Yes both of the studs have rubber insulating washers to isolate the casing