Prestolite alternator

[MikeBz]

This is a Prestolite alternator (no model/part number visible) from a friend’s MD22L engine.



There is no terminal labelled D+, but there is a D-. The only mention of D- I can find anywhere says “In some systems, particularly older marine or industrial units, the regulator might have an "E" or "D-" terminal to ground the regulator”. In the pic I’m guessing that D- is the black wire going to a spade terminal and D+ (charge indicator) is the stud terminal to its right?

The boat has an Adverc Battery Controller fitted so I’m guessing the green wire coming out of the regulator is to allow the Adverc to control the field current.

 

[Boater Sam]

This is a Prestolite alternator (no model/part number visible) from a friend’s MD22L engine.

View attachment 198821

There is no terminal labelled D+, but there is a D-. The only mention of D- I can find anywhere says “In some systems, particularly older marine or industrial units, the regulator might have an "E" or "D-" terminal to ground the regulator”. In the pic I’m guessing that D- is the black wire going to a spade terminal and D+ (charge indicator) is the stud terminal to its right?

The boat has an Adverc Battery Controller fitted so I’m guessing the green wire coming out of the regulator is to allow the Adverc to control the field current.

Colour blind? I can see no green wire, only blue and black.

 

[MikeBz]

Colour blind? I can see no green wire, only blue and black.

It looks green on my screen, but having now seen the unit in the flesh it is indeed blue!

 

[PabloPicasso]

I hope this helps

 

[Graham_Wright]

There is a big fat terminal labelled +.
You might have fun exciting it.

 

[PabloPicasso]

I remember having difficulty as what looked like D- actually turned out to be D+ when looked at more carefully from a different angle .

 

[MikeBz]

Interesting. Maybe just a badly stamped casing.

 

[PabloPicasso]

Give it a wipe/clean, try lighting it from a different angle.

Check with the diagram too.

You want to be sure to be sure, sure you do.

If you can find the prestolite part number you might be able to get the specific diagram for your alternator.

If you google "prestolite alternator diagram" you'll get pics of several different types. Just try and find a match for the layout of yours.

You really do want to wire the connections correctly

 

[Boater Sam]

Interesting. Maybe just a badly stamped casing.

View attachment 198849

Cast, not stamped. Prestolite have a good customer service system with mobile engineers, a phone call to them may solve the dilema.

 

[PabloPicasso]

Give it a wipe, try lighting it from a different angle.

Check with the diagram too.

You want to be sure to be sure, sure you do.

If you can find the prestolite part number you might be able to get the specific diagram for your alternator.

If you google "prestolite alternator diagramyou'll get pics of several different types. Just try and find a match for the layout of yours.

 

[MikeBz]

We have pictures from before everything was disconnected so can reconnect as-was, I was just curious as o why it has a D- on it. The rear pic of 66021151M says “wire from B- to D-“ just to add a bit of confusion.

We took the alternator off as it has stopped working, turns out it was just worn out brushes. We could have checked/fixed that just by removing the regulator instead of first wrestling the whole unit and its bracket off the engine (not possible to get the long bolt that it pivots on out without taking the bracket off). Hey ho.

 

[yotter]

I have a Prestolite 100A alternator on my MD2030, it is very good apart from being white and not green I would calling the alternator and starter company based in Plymouth UK, very knowledgeable and helpful. no connection
Angus

 

[PabloPicasso]

Does this help?

Google-Ergebnis für https://tradeservice.eu/media/catalog/product/cache/a406c04de1281a8e36a4fd21b07af5b7/p/6/p66021151m_dim_r.jpg

It does look like the layout of your alternator?

 

[PabloPicasso]

This is a Prestolite alternator (no model/part number visible) from a friend’s MD22L engine.

View attachment 198821

There is no terminal labelled D+, but there is a D-. The only mention of D- I can find anywhere says “In some systems, particularly older marine or industrial units, the regulator might have an "E" or "D-" terminal to ground the regulator”. In the pic I’m guessing that D- is the black wire going to a spade terminal and D+ (charge indicator) is the stud terminal to its right?

The boat has an Adverc Battery Controller fitted so I’m guessing the green wire coming out of the regulator is to allow the Adverc to control the field current.

Is the part number printed in white in the pic (VR-B195MN500421)?

 

[Graham_Wright]

Again! The positive terminal is the big fat one!

 

[MikeBz]

Is the part number printed in white in the pic (VR-B195MN500421)?

There is a label on it with Prestolite and spaces for part no etc but no actual information.

Again! The positive terminal is the big fat one!

Yes. Curiosity was about why it has D- on it. But anyway it’s now had new brushes and has been tested at Nacton Autoelectrics in Ipswich. All we have to do is refit and reconnect as it was originally.

 

[PabloPicasso]

There is a label on it with Prestolite and spaces for part no etc but no actual information.

Yes. Curiosity was about why it has D- on it. But anyway it’s now had new brushes and has been tested at Nacton Autoelectrics in Ipswich. All we have to do is refit and reconnect as it was originally.

Yes, very curious. Was it just poor casting? Or is it a D-?

You could ask the people who tested it

 

[Graham_Wright]

D- might refer to the fact the alternator has an isolated output, i.e. the negative is not connected to the frame.

 

[PaulRainbow]

D- might refer to the fact the alternator has an isolated output, i.e. the negative is not connected to the frame.

No, that would be a B- terminal Graham.

 

[MikeBz]

I think it’s just a poor casting as otherwise it is identical to the pic in post #4. I will be briefly reunited with it on Tuesday to refit it, but let’s just say that the owner is dead chuffed that it cost £34+VAT to repair and test.
For a replacement, had that been necessary, he was quoted £500 by a Volvo parts supplier/engineers for a new alternator (also available elsewhere for not much over £100).