I know this thread is old and probably original reporter's problem is already
solved, however my information may help someone else with a similar problem.
The described problem: System voltage when
charging is too high, The ARS-5 says Bv is lower than what is measured at the buss, or house bank.
Possible cause: A resistance in the sense wire (red wire) from the buss to the regulator is causing a voltage drop. The regulator sees a lower voltage and kicks up the alternator , causing too high system voltage.
Verification: Measure the sense wire voltage at various points from the buss to the red lug on the ARS-5. If you see any significant drop in the measured voltage than this confirms a resistance. Perform this test while charging because
current flow through the wires usually magnifies the voltage drop.
Cure: Replace the sense wire. Do not install a new sense wire without a fuse in it. The fuse is needed to protect the ARS-5, however, be careful you don't reuse the fuse holder if that is the source of the voltage drop.
Note: I have seen the resistance occur at the fuse or fuse holder in the sense wire, sometimes a voltage drop of .8 - 1.2 volts. which is enough to throw off the whole regulation system