300TDi Alternator Charging but Battery Light Glows

I’m a bit stumped and would appreciate some assistance. The battery light of my 97 Defender 90 recently started glowing, but the vehicle kept starting and the headlights stayed bright. Nonetheless, I replaced the alternator with a John Craddock spare, but the problem remains. On examination, the output on the B+ terminal is a bit over 13V with the engine running, but the voltage from the D+ terminal to earth on the chassis is 6.5V. I’ve tested the continuity of the brown/yellow wire from the D+ terminal to the block connector on the bulkhead, and it is good, with no earth leakage. Is there a diode or resistor that I’m missing, or some other issue?

Thanks in advance.

The diode in in the unit on the back of the alternator.

Many thanks - you’re spot on. John Craddock exchanged the alternator without question, and the replacement works perfectly. In the meantime, I’ve now got the cleanest wiring loom in the business, with every contact gleaming, but it was a good opportunity to brush up on my vehicle electrics.

Nice to know your sorted.