Interesting.
When I got my 3B, the Hi Beam indicator didn't work. Found the wire had been disconnected under the hood.
Why?
Which ever PO converted from 6V to 12 V didn't switch the bulb in the indicator.
Why?
The housing of the indicator was rusted together and I couldn't get it apart to change the bulb.
So
I just put a resistor in series with the wire out by the headlight terrminal block. So now the 6V bulb glows nicely in a 12V system without blowing out.
If anybody wants to know the value of the resistor, I'll go back and look at what I put in (4 years ago) and post it.