You'll have to use the diode test on the multimeter and not the continuity test. Right off memory I think it shows this kind of symbol: ->| . Also you will need probably need to unhook the wires the diodes are on to be sure you dont bypass them when testing.
Diode Test
The manual says you have a solid state voltage regulator as lochlin said so there are no adjustments. If the diodes test good then I would say you need a new voltage regulator.