Defender 10 FFR Alternator 24v 90 Amp

Hi all
I recently had batteries installed in rear (2 12v batteries and a 24v power inverter) of my 110 FFR so that I could run radio, lights, TV etc. All worked fine and auto electrician stated that the alternator was charging at 27.2V. All ok.

Had new drive belt fitted yesterday now 24V warning light is showing and electrian says that no charge is coming through.

Light did go out briefly this morning on motorway when speedo said 100km per hour(that's what it reads) but came back on when left motorway and back down to 50km. Can anyone offer any suggestions or an alternative 24volt alternator

Is the fan brlt on? Using a multimeter check if voltage is o the genny cintakt to gnd with the gand throttle reving . Look at ameter installed zero or charge , no rafios switched on! Now check that the connectors are tight on regulator box behind seat check correct connecyion of the chsrging cable from the regulator to battery bank check that 24v batterys are grounded. Little tip from me fit 100A fuses to all batteries , 12v and 24v , another tip from me arange a switch to break the middle connection of the 2 x 12v making 24v to allow you to connect this to the vehichle battery so giving you a jump start if needed having one genny running with 24v and the alternator runni g with 12v is ok for a while as the second battery is still connected, when started break the switch to revert to correct charging regulation. This has saved my but a few times! I have found electrical service box main switches like the ones used in 240volt ac house fuseboxes fit for purpose and good cheep technology, actualy better than vehichle types

In the unlikley event that you have blown the diodes in the 24v genny you can replace them with new ones from rs components. Is the regulator relay with clean contakts?