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Joined: Apr 23 2019
Posts: 539

I must be bored, but my alternator kicks out anything from 13.7 to 14.0 (scraping 14.1 sometimes). I have an S4 Bosch battery (which says that the min voltage shd be 12.4V to avoid damage). It's hard to figure out if the Bosch (Varta) battery contains calcium - multiple searches are completely silent - so I guess that means not, although Battery Megastore says it is - Bosch themselves don't seem to say

I'm obviously not getting to drive it much these days, but battery voltage falls below 12.4V fairly often - that said, I never have problems cranking. If the voltage drops then I chuck it on a smart charger every few weeks, and now I have a solar panel on the parcel shelf (jury's still out on that). Guessing that my set point is about 14.0V currently (which I think was on spec for the year/model) then should I look for a VR with a higher set point ? Does anyone have a positive ID on one?

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Joined: Feb 11 2018
Posts: 357

I don't have id but I used this site to cross reference for mine on a m51 diesel.

https://en.as-pl.com/index

https://en.as-pl.com/p/A4100

https://en.as-pl.com/p/ARE4005

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Joined: Feb 11 2018
Posts: 357

Need to look for ones that specify set point of 14.4 or higher. Some don't.

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Joined: Apr 23 2019
Posts: 539

Thanks Tanis. I've found a 14V replacement for the AMR4272 100A (MM no was RTM 153B) - the 120A AMR 2938 is proving more elusive though - I pulled the alternator off, and the regulator has RTM123A on it. I've sightly given up on the higher set point notion, although the old MM ones simply have a std voltage regulator soldered in, so I briefly entertained the notion that I could solder in a new one with a higher set point, but then remembered I have a near-zero chance of ever finding said component and I have better things to do with life. I guess it's not impossible that a PO replaced the alternator at some point, either, so I may be chasing shadows

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Joined: Feb 11 2018
Posts: 357

No problem

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Joined: Apr 23 2019
Posts: 539

For anyone still reading - turns out my AMR 2938 is not a 2938, and the case is stamped 54022544 A127 120A. I'm currently trying to figure out what the hell it is/ where it came from... something that Solihull had left over, or a later addition. All I really want is to replace the VR - although after cleaning up the slip rings she seems to hit 13.9/14 much more consistently, so the current one is more workable now. Unless anyone collects rare alternators ?

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Joined: Dec 30 2015
Posts: 4732

I'll have a look at the numbers on my old one tomorrow. My car is also a 98 and I suspect plod would have specified the 120A option. It died a couple of years ago after around 300k miles but it's on a shelf in the garage waiting for the time I decide whether to sling it or get it reconditioned.

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Joined: Dec 30 2015
Posts: 4732

Best I can manage I'm afraid, can't find an LR number on it anywhere......

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Joined: Apr 23 2019
Posts: 539

Thanks for trying Richard

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Joined: Apr 23 2019
Posts: 539

So for anyone following: for my AMR4247 (mine is on the Defender, but it is also the 100A on the earlier Gems V8s), I was sent a Transpo IX123 after following a trail of ref numbers, but that just has a standard set-point. I guess the challenge is that these manufacturers are used to copying the spec of components, but finding the right ref for an upgrade set-point can be a challenge. Sort of what Tanis was warning about further up

However, a Mobiletron Vr-F153a fits and has a 14.7v set point - lovely...

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Joined: Feb 11 2018
Posts: 357

All info that's useful.
Glad you got one :)