Battery not Holding Charge Land Rover 90 1989

Hi I’m new to this community, and relatively new to the realm of ownership of a 1989 Landi 90 with a J Series drive train, having now owned my piece of British history for over a year now and boy have I entered a world of expense, frustration, head scratching and admiration for the brand.

So amongst a number of challenges the truck has, my top one is my battery doesn’t hold its charge, especially in the cold periods we are now in and I’m having to keep charging the battery up every few days or so.

Since owning the truck the battery symbol on the dash hasn’t illuminated despite changing the bulb. I have checked the battery following a full charge’ and is at the right recommended level. However having checked the battery whilst engine idling ‘to check the alternator, it’s below the recommended level sitting at 12.85.

I am not mechanically minded and will give anything a go, except when it comes to auto electrics. So would this be as simple as an alternator swap out, although the one Im my truck looks relatively new…..

Hope anyone can provide some advise…..thank you and Merry Christmas

Welcome.

Photo of the alternator will help(just in case they have been modified)
The battery light should be on with ignition,this is what starts the charge on certain alternators

With the engine running [ little bit on the throttle] a good alternator will give 14v or there about on your volt meter.

You'll have to identify if you have a 2 wire, 3 wire or 4 wire alternator. If you have the 3 or 4 wire then the alternator will detect that the battery is full and you won't necessarily see a 14v charge being sent to the battery while running. If you have a 2 wire then there is no Sensor terminal and the alternator will send 14v regardless.

Also bear in mind that a battery reading 12.7 volts may seem healthy but the cranking amps can be knackered. Unfortunately a multimeter can't tell you that reading, you'll need either a battery health tester, or a load tester.

Recently my vehicle was acting up and the battery was dying all the time, battery light never lit up. According to the multimeter it seemed like the battery, but the load tester said it was in good health. So I replaced and upgraded the alternator from a 2 wire to a 3 wire (with S Terminal). All good now.