Alternator case fix questions

[Bucket T]

I have an alternator that a mounting tab broke off. Can the aluminum case be welded or fixed with JB weld? It's for my 71 Datsun and I'd rather not use it as a paper weight. 

[1930fordpickup]

I think you will have to get a new case for that. I don't believe JB weld would hold for very long.  Do you know anyone that welds aluminum? 

[GMP440]

JB Weld will not hold.  You need to get someone to tig weld that back on or as stated by someone else, get another case.  Rock Auto has no Datsun listing but there is Nissan which owns Datsun.   Here is a link for alternators if that helps.

https://www.rockauto.com/en/catalog/nissan,1971,521+pickup,1.6l+l4,1212321,electrical,alternator+/+generator,2412

[Ace-Garageguy]

JB Weld? Nope. Though it'll work for some stuff, it won't work for that. It's just glue...not a structural repair.

Though aluminum castings like that can be welded, unless the welder really knows his stuff, and can get pretty close to the original material for filler rod, it'll quite likely fail again right next to the weld.

And because the long mounting bolt needs to be accurately aligned on both ends, the welder will have to take extra time to jig/fixture the part prior to welding...and most likely, at least a small amount of machine work will be necessary afterwards.

To fix that correctly, both sides of both parts need to be tapered to a vee, the broken ear needs to be jigged in place, and beads need to be laid on both sides of the vee'd joint. There may be some movement of the ear during welding, so the hole may need to be trued afterwards, and any weld buildup on the milled faces of the ear need to be machined off. 

Also note that unless the ear is welded dead square with the housing, additional force will be placed on it when the mounting bolt is tightened down, which can lead to another failure.

Because I have in-house TIG capability, if it were mine, I'd give it a shot, but I'd be prepared to replace it in the event welding wasn't successful.

You can buy an entire replacement for anywhere from about $70 for aftermarket of questionable quality (and cheaper than fixing that case right, unless you know a really good welder who'll do you a deal) to around $500 for a genuine Nissan OEM part.

EDIT:   https://www.motortrend.com/how-to/syncrowave-210-miller-electric-shows-how-to-tig-weld-cast-aluminium/

Edited April 28 by Ace-Garageguy

[fordahaulic]

also before welding it will need to be disassembled. the current of the welder will burn out the diodes. you might be able to find a decent one from a salvage yard.

[Big_John]

IMHO, epoxy will fail almost immediately, so that's  not an option.

If you had access to TIG weld it, I'd say to try it, but if you have to pay for it, it's going to surpass the cost of a rebuilt piece. 

I did a quick search and there's replacements on eBay for around $50.  I can't say anything for quality, but save that working alternator and you can swap parts if it lets you down.   Which brings me to another suggestion... If you can find a used alternator cheap, it's not hard to swap the case. 

[Daddyfink]

Maybe it is time to upgrade to a newer alternator. 

You might find the info you seek here..

https://ratsun.net/forum/19-electrical/

[Ace-Garageguy]

18 minutes ago, Big_John said:

...but save that working alternator and you can swap parts if it lets you down...

On the surface that's not a bad idea. 

However...the reality of aftermarket parts is that they're almost never made to OEM specs, so there's no reason to expect the OEM guts will fit an aftermarket housing...unless you buy a rebuilt unit you KNOW was built in an OEM housing.

Sorry, but that's just reality in the car biz.

HOWEVER...the idea of finding a cheap used unit, even not working, is excellent.

Clean it up, swap the parts out, replace the bearings and slip-brushes (rebuild kits should be available), and you're golden.

Edited April 28 by Ace-Garageguy

[stitchdup]

if you have a part number i can probably find you a casing, but i'm in scotland. i do have access to my friend that passed a couple years ago workshop. he did starter and alternator repairs and theres a shipping container packed with very late 60s-00s alternator and starters for euro and jap engines and marine diesels. if you cant find one close to home it could be an option. my sister inheritted it all and i convinced her to not dump any of it. i can even supply earlier dynamo casings. most of it is nos parts too.

[Tabbysdaddy]

Yeah, I would buy a new alternator or at the minimum buy the case. 

[Big_John]

2 hours ago, Ace-Garageguy said:

On the surface that's not a bad idea. 

However...the reality of aftermarket parts is that they're almost never made to OEM specs, so there's no reason to expect the OEM guts will fit an aftermarket housing...unless you buy a rebuilt unit you KNOW was built in an OEM housing.

 

The ones I looked at on eBay were "remanufactured" Hitachi units, so I assume that would be what the OEM used. 

Are they actually offering new units that cheap?  I'm not doubting that an aftermarket alternator might be different enough to not allow much parts swapping.  

Cheapest on eBay.  https://www.ebay.com/itm/204485279667?fits=Year%3A1971|Make%3ADatsun&epid=227430304&itmmeta=01HWKB54MFW612FJSBA5XPX1H1&hash=item2f9c45bfb3:g:EJQAAOSwje1lxVD5&itmprp=enc%3AAQAJAAAA8ClgJZGL%2F71FGbLrTazEygwB%2B9shABs8jxWsqVCqLHzfCuPdR50VecVd0%2BrOxQRESIP82yqHLccmJofF1skIN0RFcB9osSKrpjaALm7r38UVKgceN%2BzCYLPhz86NecR4KXeAO97F9ZejVWNtAHfCWZEO5IY3VvPU18MNuOtuQBEskTJ%2Bhx8VlezEnrj6bqW5DcqErxDha4BWKto7tcPu%2FXqGc%2BrjJ%2FTSAX5ZX0bNOuECbmYbOT5N6Xiiii%2FKolBYxGUmWcc2ZESN7iLYry0NfZfwBXzT4lJClmL0Gtb6Jp6AIRE2mf1Wx3tZV5g0PFxS0A%3D%3D|tkp%3ABFBMssqU6-Rj   

Is that an aftermarket or rebuild? 

 

 

[Ace-Garageguy]

1 hour ago, Big_John said:

The ones I looked at on eBay were "remanufactured" Hitachi units, so I assume that would be what the OEM used. 

Are they actually offering new units that cheap?  I'm not doubting that an aftermarket alternator might be different enough to not allow much parts swapping.  

Cheapest on eBay.  https://www.ebay.com/itm/204485279667?

Is that an aftermarket or rebuild? 

The one you put up is a reman.

However, new ones are available for not much more...    https://www.ebay.com/itm/285798980447?

                                                                                                https://www.ebay.com/itm/266725529302?

Edited April 29 by Ace-Garageguy

[Oldriginal86]

We use a local electrical shop for our alternators, starters and thruster motors. There is a large basket full of end frames for alternators. Should be a shop that rebuilds this stuff near you that can put a new housing on.

[MeatMan]

On 4/28/2024 at 12:53 PM, Bucket T said:

I have an alternator that a mounting tab broke off. Can the aluminum case be welded or fixed with JB weld? It's for my 71 Datsun and I'd rather not use it as a paper weight. 

 

I agree with those who say replace the housing. I used to do that when I worked at a parts store during the time frame that Datsun was new and its not that difficult to do. If you can find a good housing, any decent back yard mechanic can do it. They just have to make sure they use the proper method to secure the brushes prior to separating the halves. Good luck.

[Bucket T]

All good advice. And prices that won't break the bank. I know someone who might be able to weld it but as Bill said it most likely will fail again.  Thanks guys

  

[Ace-Garageguy]

Just a thought...and I haven't been inside an old Nissan alternator in decades...be sure to check the diodes one-at-a-time if you have it apart.

One bad diode and it won't charge at max output, if at all.

Again, I don't remember this particular unit, but diodes in alternators very often require a special press-tool to remove and install them with no damage.

You do NOT want to hammer one in if you need to replace it.