Sorry Doctor its my alternator again.

[rogerball0]

Above is the wiring diagram of my alternator, below is the actual back of it, what i'm still sruggling with is theres no defined negative terminal on the back or rather where there should be is blanked off with a bolt, when Tony and i fired it up the other day i put the battery negative on the top left stud to the left of the terminal marked 'W' which is one of three that holds the alternator together.

The last time i fired it up the battery light was flickering on the instrument panel and the engine was hunting quite noticably from 700 rpm to 1200 rpm so think its electrical, i put the multimeter on the battery and the charge was slowly going down as when the engine was first fired it was reading 13.8V and by the end with engine running constantly the battery was down to 12.1V so presume the alternators not charging the battery.

Is it a case of removing the bolt on my alternator and simply putting a stud in there to make a negative stud as per the diagram of mine or should it stay where i put it on the top left stud.

EDIT: Have just removed the bolt where the negative stud is shown on the diagram and it looks like a chipboard screw with a head of a bolt on it so dont know what to do?

Cheers

Roger

 

[mjcoon]

Um. Your diagram shows a negative terminal at the 5 o-clock position just under the output connections.

Quite, as in "... there's no defined negative terminal on the back or rather where there should be is blanked off with a bolt, ..."!

Mike.

 

[twohats]

Is that a Prestolite?
Put your multimeter between the battery negative terminal and the alternator case while charging to check if there is excessive voltage drop in the negative circuit.
If you need to add a connection direct to the alternator case you could put a ring crimp under one of the three nuts holding the case together. The bottom left one looks a good bet. Or else a large ring crimp under one of the main mounting bolts.

 

[prv]

If you need to add a connection direct to the alternator case you could put a ring crimp under one of the three nuts holding the case together.

??

He said he's already tried that.

Pete

 

[rogerball0]

Is that a Prestolite?
Put your multimeter between the battery negative terminal and the alternator case while charging to check if there is excessive voltage drop in the negative circuit.
If you need to add a connection direct to the alternator case you could put a ring crimp under one of the three nuts holding the case together. The bottom left one looks a good bet. Or else a large ring crimp under one of the main mounting bolts.

Yes its a prestolite, heres the page on their site of my alternator: http://www.prestolite.com/pgs_products/specs.php?item_detail_id=13070&item=66021126#

??

He said he's already tried that.

Pete

Have run out of ideas as i'm not very clever, will give the bottom mounting bolt a go afteri've i've finished with the wiring, but please keep the ideas and suggestions coming , very much appreciated.

cheers

 

[pvb]

You can connect the negative to the alternator case, or it may earth OK through the mounting bracket anyway. Are you connecting a wire to the IND/D+ spade terminal?

 

[Birdseye]

The marine version with the isolated earth is 66021151M. As it happens I have been looking into fitting one of these to my boat and Prestolite just sent me a pdf of the current model. The back of it doesnt look like your photo or indeed the drawing so I wonder if the alternator you have been sent is the non marine version that earths through its frame. If you pm me your email I will send you the pdf file that Prestolite sent to me. Or if you want to contact them direct the UK technical guy is NJepson@Prestolite.com

 

[pvb]

The marine version with the isolated earth is 66021151M. As it happens I have been looking into fitting one of these to my boat and Prestolite just sent me a pdf of the current model. The back of it doesnt look like your photo or indeed the drawing so I wonder if the alternator you have been sent is the non marine version that earths through its frame. If you pm me your email I will send you the pdf file that Prestolite sent to me. Or if you want to contact them direct the UK technical guy is NJepson@Prestolite.com

You don't have to have an insulated return alternator; most boats don't.

 

[G12]

The W terminal is for connecting a rev counter!

B+ for the output to the battery and the negative should be grounded to the DC ground (it's possible to ground it to the engine block if it has a good earth). The D+ excites the alternator.

 

[rogerball0]

Brilliant job lads, have just got off the phone from the tech from prestolite who's explained pretty much the above. He told me its an 'earth-return alternator' where a negative isn't req'd/available so although he said i could reinstate a stud where the screw-type bolt is on mine i should go for either on the engine block where theres a big black-painted bolt or on the bottom of the mounting bolt would be sufficient (the one that carries the spacers) or anyone of the three assembly bolts of which one we used.

My money' on either the block or the bottom bolt as thats a nice big M8 same as the block.

PM sent Birdseye cheers.

I'll get it wired back up tonight and fire it up over the weekend and report back, although anymore ideas on this to aid my limited knowledge is always welcome.

 

[Spyro]

You don't have to have an insulated return alternator; most boats don't.

I've just fitted a new alternator and was told by two sources that most boats do. I'm sure this is going to start a good debate.

 

[pvb]

I've just fitted a new alternator and was told by two sources that most boats do. I'm sure this is going to start a good debate.

Your sources misinformed you! Boats with metal hulls may benefit from an insulated return alternator. The vast majority of boats don't need one, and don't have one.

 

[Tintin]

Your sources misinformed you! Boats with metal hulls may benefit from an insulated return alternator. The vast majority of boats don't need one, and don't have one.

mmmm not sure I agree with that - my current boat (beneteau first 325) had insulated -ve, my last boat had insulated -ve (Leisure 27), and if my memory serves me right, every other boat I have had cause to poke around with the aternator has also had the same, but of course I may be confused as it is late

 

[pvb]

mmmm not sure I agree with that - my current boat (beneteau first 325) had insulated -ve, my last boat had insulated -ve (Leisure 27), and if my memory serves me right, every other boat I have had cause to poke around with the aternator has also had the same, but of course I may be confused as it is late

YMMV

 

[Tintin]

YMMV

Gosh, I thought I was pretty hip and cool (errhem) but I had to google that

 

[Spyro]

mmmm not sure I agree with that - my current boat (beneteau first 325) had insulated -ve, my last boat had insulated -ve (Leisure 27), and if my memory serves me right, every other boat I have had cause to poke around with the aternator has also had the same, but of course I may be confused as it is late

My Jeanneau had insulated -ve I'm sure they know what they are doing.

 

[pvb]

Gosh, I thought I was pretty hip and cool (errhem) but I had to google that

 

[JumbleDuck]

Is it a case of removing the bolt on my alternator and simply putting a stud in there to make a negative stud as per the diagram of mine or should it stay where i put it on the top left stud

Looks to me as ff the case is grounded, so just use any of the three studs at 3, 7 and 11 o'clock.

 

[mjcoon]

Gosh, I thought I was pretty hip and cool (errhem) but I had to google that

"YMMV" dates back to USENET, so there's such a thing as being too cool and up with it (or up something!)...

Mike.

 

[Tintin]

"YMMV" dates back to USENET, so there's such a thing as being too cool and up with it (or up something!)...

Mike.

Phew. I was worried for a while there.