wheeler wrote: 23 Feb 2024, 07:49
Meter leads across the 2 battery terminals = battery voltage
Meter positive to battery + terminal & meter negative to alternator casing = battery voltage
Meter positive to alternator positive connection & meter negative to battery negative terminal = battery voltage
Meter positive to alternator positive connection & meter negative to alternator casing = battery voltage
If the wiring is good all these scenarios should give the same voltage reading on your meter.
Repeat the last scenario with the engine
running & if the alternator is working you should get over 14v
Do all the scenarios above & note which ones do not give the same as the battery voltage.
The big terminal on the alternator is directly connected to the battery positive & the casing is connected to the negative hence the reason you should get the same voltage reading direct at the alternator. If there is a difference (and assuming you are making good & correct connections) there could be an earthing issue.
Do you have jump leads? if so take the black one only & connect one clamp to the battery negative terminal & the other one to a good bare metal bit of the engine (engine mount bolt is ideal, see pic).
once this is connected re check the battery voltage with the engine running.