Ross8799 Posted December 16, 2023 Share Posted December 16, 2023 Ive got a 2012 Land Rover Defender. The dash shows the battery warning light even after the battery has been replaced. Not sure if this is connected but the headlights have been dimmer as well lately. I'm looking for suggestions to problem solve this please. Quote Link to comment Share on other sites More sharing options...
Retroanaconda Posted December 16, 2023 Share Posted December 16, 2023 The battery warning light is not to indicate problems with the battery, more to indicate problems with the charging system. Use a multimeter at the battery with the engine running to see what voltage your alternator is producing, I suspect it is not charging properly. 1 Quote Link to comment Share on other sites More sharing options...
Snagger Posted December 18, 2023 Share Posted December 18, 2023 Dash battery warning lamps do not indicate anything to do with the battery condition - they merely indicate that it is being discharged via the ignition circuits instead of charged (doesn’t even show whether other circuits discharging the battery). This is because the battery is feeding the alternator exciter coils via the lamp circuit but the alternator is not providing an opposing charge to cancel out the current and extinguish the light. That is what happens if you switch on the ignition but don’t start the engine on an healthy system - the alternator coils are energised by the battery but the alternator is not providing any charge. Its illumination is rarely caused by the battery itself. If your dash light is on when the ignition is switched off, then you have a fault in the ignition switch and it is permanently live. If it is on while the engine is running, you have a problem with the alternator (could be the unit itself, its diode pack or just a slipping belt), assuming you don’t just have a short in the wiring behind the dash. I’d check the belt is good first, then I’d suspect the diode pack (really need to swap the alternator for a good one to test that, unless you can take it easily to an autoelectrician who can test it for you). Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted December 19, 2023 Share Posted December 19, 2023 18 hours ago, Snagger said: If your dash light is on when the ignition is switched off, then you have a fault in the ignition switch and it is permanently live. This can also be a faulty diode pack in the alternator, depending exactly how it's wired... some Defenders put an anti back-feed diode in the warning light circuit but I don't know if that's universal. Quote Link to comment Share on other sites More sharing options...
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