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Alternator replacement - connections?


WJM

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I am planning to replace my alternator. The new one has arrived and it seems to have a lot more electrical connection points than the old one. I need some advice on how to connect the new one up. Presumably the thick cable is the one that takes the power away. Where on the new alternator should it go. And the thin spade-connector cable, what is it for and where should it go? Thanks in advance.

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The thick cable to the battery positive will go to B+. The cable to the ignition warning light, which is the thin one, will go to D+ The cable to the tachometer, if fitted, will go to W, but it doesn't look like you have one of those. In addition, you will need to add a new cable of the same size as the B+, but black. This will need to go between the B- connection and the engine block on to a suitable bolt. The engine block should also have a thick cable already connecting it to the battery negative. The previous alternator was earthed through the case and attachment bolts. This one looks to have a separate earth, but may, or may not be. Do you have a make and model number for the new alterntor, so we can check?

Jen

Edited by Jen-in-Wellies
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3 minutes ago, WJM said:

Thanks for the speedy reply. The new one is BA030-2005. 

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By the way, there is a cable already connected, joining the B+ and the B- and it has a little sealed black box at one end.

That is a capacitor probably for Radio interference suppression 

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Rather than connect a heavy wire between B- and a bolt on the engine, you could remove the insulating washer from under the B- connection to earth it to the body directly.

The plastic box is a suppressor to enable the radio to work without interference, you probably do not need it.

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8 minutes ago, Tracy D'arth said:

Rather than connect a heavy wire between B- and a bolt on the engine, you could remove the insulating washer from under the B- connection to earth it to the body directly.

 

The body of the alternator seems to be heavily painted or anodised. But I suppose I could scrape back to bare metal. Would that work?

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6 minutes ago, WJM said:

I can’t find an exact match on the Prestolite site. But I did find this on a Google search.

 

https://www.adesas.co.uk/product/171/?doing_wp_cron=1615657893.4654760360717773437500

Looks to be one of the AS128 series. Which one, I've no idea!

https://www.prestolite.com/pgs_products/n_alt_results.php?pf=true&item_series_id=116&series_name=AS128

1 minute ago, ditchcrawler said:

I think I would go for the earth strap in case you happen to have a warranty claim 

One of these braided earth straps from B- with the insulated washer to one of the alternator mounting bolts would do the job fine.

https://www.halfords.com/motoring/battery-maintenance/battery-accessories/halfords-braided-earth-battery-cable-22cm-9in-165332.html

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1 minute ago, ditchcrawler said:

I think I would go for the earth strap in case you happen to have a warranty claim 

That is what I would do, but the strap woulld go back to the engine bonding point, or if there isnt one back to the battery.

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3 minutes ago, Loddon said:

That is what I would do, but the strap woulld go back to the engine bonding point, or if there isnt one back to the battery.

There will almost certainly be an engine bonding point for the starter motor to work. We know the previous alternator is earthed to its frame.

Edited by Jen-in-Wellies
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31 minutes ago, WJM said:

The body of the alternator seems to be heavily painted or anodised. But I suppose I could scrape back to bare metal. Would that work?

10AE999B-5FB8-49BB-A6C1-C41720326817.jpeg

Yes.  Keep the insulated washer in case you need it, I would add it to one of the other terminals for safe keeping.  Put the steel washer back on the B- with the paint scraped off.

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