240 D24 Alternator Options
 

Can any of the below alternators work in a 240 D24 NA without any modifications (plug-n-play, maybe except for swapping the pulley)?

Also need it to be compatible with the tachometer.

80A Bosch
https://www.fcpeuro.com/products/vol...-dl-745-al157x

100A Bosch
https://www.fcpeuro.com/products/vol...780-940-al155x
Same as this on Ebay, I believe: https://www.ebay.com/itm/25482654086...gAAOSw8-Rf9MBu

100A Nippon-Denso
https://forums.turbobricks.com/showthread.php?t=282770

140A Bosch
https://www.ebay.com/itm/140-Amp-Vol...-127632-2357-0

The tach wants the "W" terminal on the alternator. Do any of those have a W terminal?

Otherwise, you could add the W terminal with a little surgery:
Gas Tacho / Revcounter Conversion to Diesel W terminal

And there are YT videos showing how.

I ended up having my bad alternator rebuilt at a local starter/alternator (in-house) rebuild shop. PIA to deal with the know-it-all grumpy guy but he did a good job.

The design of the alternator case might also be a factor (whether it is able to bolt in to the factory bracket). I don't think any of those that you linked to are the same size/design as the factory 55A alt.

If the goal is adding higher output, I wonder if a clever enough rebuilder would be somehow able to upgrade or hot-rod the factory style alternator? Maybe use the back half of some other alternator built into the front bolt-on case from the factory style?

Or if you are going to go to the effort of reengineering the system to add output, another option rather than trying to swap a different alternator in place of the factory one would be to add a second alternator somewhere instead. Maybe right above the factory alt since on a nonturbo D24 that doesn't have the turbo inlet in the way, I think there is some extra space available there. Some heavy duty pickups (Ford Powerstroke, GM, etc) offer dual alternators as an option for applications that have heavy electrical demand like emergency vehicles so it is a concept that is known to work well. As a side benefit the second alternator gives some redundancy.

You would of course need to fabricate a custom bracket for that and need to think about how it would work in terms of running the belts. But it might be an interesting alternative, and it would also save you from having to worry about the W terminal or pulley diameter for the tach since you would still have the stock diesel alternator in place to handle those tasks, and could use any other alternator as your secondary regardless of it having a W output.

That was the main reason I had mine rebuilt. Too hard to figure out if the mounting ears (on the candidate alternators) were the correct dimensions and locations.

To really make use of a higher amp output alternator will require rewiring the stock Volvo accessory wiring with heavier gauge.