<VV> ARGH!!! Simple electrical stuff driving me crazy!

[Bill Elliott]

Working on the ex-Moody Corvair/VW Westy... I can usually do electrical work in my sleep, but this one is getting to me!

Situtation before:
Stock Corvair alternator and regulator, single battery. Original GE incandesant headlamps. Voltmeter hooked to front wiring bus, no significant drop when 
headlights turned on. 12.5V with the engine off, 14V with the engine on.

Step 1:
Added H4 headlights (but stock 55/60W bulbs). Used high beam signal to trigger relay to power driving lights (sourced via dedicated line to main battery). 
No other changes... small voltage drop (0.5v)  when headlamps turned on, but voltage still above 13V running. Would drop just below 13 if driving lights 
activated.

Step 2:
Added Aux battery. Used Isolator designed to keep aux battery from discharging main battery, but allowing both to charge on the alternator. Known 
"attribute" that isolator will cause a 0.5 to 1.0V drop. 

Only  wiring changed is that the main line from the alternator to the battery was cut at the battery and run to the isolator with the old line attaching to the 
battery run to the "main battery' terminal of the isolator. Disconnected driving lights power source as I intend to power those from the aux battery... and 
wanted them out of the equation.

New situation: Front wiring bus now drops 2 full volts when the high beam headlamps are turned on. This whether the engine is running or not. Engine 
running headlamps on front bus is at 11.5V. Battery still reading 13.1

So I unhook the isolater and put the electrical system back just as it was before. No change from the new situation... front bus now dropping to 11.x volts 
with headlamps on.

Getting tricky, I move the battery wire from the regulator (in the stock system this is spliced into the alternator to battery wire) and ran a jumper from the 
regulator to the main power supply line running up to the front bus.  This removes the voltage drop caused by the isolator out of the equation.

This takes the front bus up to 14v with the car running dropping to 12.5V with the headlamps on. BUT the voltmeter on the front bus is jumping around a bit 
and the voltage back at the battery is now 16V. Possibly if I runt he jump to the battery side of the isolator I can reduce the voltage seen at the battery while 
continuing to keep the isolator volatge drop out of the equation.

So what happened between the End of Step 1 and my current problem? Did I possibly damage the alternator with too much load? Did my battery 
coinicidentally start failing? 

It's obvious that I have some harness voltage drop (~1v) between the battery and the front wiring bus... but why was that not causing a problem before?

I have a 62A Alternator to add, but wanted to solve the siutation first before I add more variables...

Anything obvious that I'm missing?

Bill