battery light

If you're handy with a voltmeter...

First, check the battery voltage when the engine is switched off. It should be around 12.5V if the battery is good and charged.

Next check the voltage at the battery terminals when the engine is running, IIRC it should be around 14V if the alternator is working properly. If it is much lower than this (~12V or less) then the charging circuit isnt working, which would be causing your light to come on.

If this is the case, check the voltage at the terminals on the alternator (disconnect the wiring from the alternator, attatch crocodile clips to the terminals while the engine is switched off, then start it up. Keep your fingers.) This should also be around 14V and shouldnt change if you rev the engine, If not then the alternator is faulty.

If you have good voltage at the alternator but not at the battery then the fault is somewhere in the wiring between the two, follow the wires from the alternator/battery and check any connectors/terminals are tight and corrosion-free.

Last time this happened to a mate it was just a nut had come off where the circuit connected up behind the engine.

HTH Andy

Hi mate ...check if the alternator is charging correctly (14.2 volts +/- 2 volts at the battery ) Also check @3,000 rpm .What should happen is once the alternator output has matched the battery voltage the light goes out ,as the exciter feed is obviously via the battery light.If not check the exciter feed ,do volt drop tests for the b+ lead and chassis earth ,If all checks out ok the problem may well be with the instrument panel as in the past ive seen the light resistor detach itself behind the clocks. let me know how you get on all the best mark

p.s nominal battery voltage is 12.80 volts 2.13 per cell x6