question on bulkhead connector bypass

What is likely happening now......and this is VERY common, is the voltage drop problem in the harness. There is a couple of issues. "What you fixed" when you did the ammeter bypass is you upgraded the charging output wire of the alternator, and the supply to the electrical loads in the car........headlights, heater, etc

BUT SOME OF THIS STILL comes back through different terminals of the bulkhead connector. ONE of those is the (normally) blue "ignition run" (IGN1) wire which comes FROM the ignition switch and supplies power under the hood to ignition, some smog devices, the electric choke if used, AND THE VR and alternator field

IF THERE IS voltage drop in that circuit the battery will overcharge, and if the connections are not stable, the flickering will result

HOW TO CHECK:
1...GROUND:
There is actually one MORE possible path that causes this, and this is the grounding relationship between battery, body, engine, and voltage regulator

TO CHECK, run engine until warm and battery is "normalized." Run engine to simulate "medium cruise" RPM. Run this check first with all loads turned off, and again with them on (heater, lights, etc)

Stab one probe of your meter into the top of the NEGative battery post. Stab the other into the mounting flange of the VR. Be sure to get through paint, rust, etc. You are hoping for a very very low reading, the lower the better, and zero is perfect

2......HOT SIDE of the harness:

To make this check turn the key to "run" with the engine stopped. Leave all wiring connected as "normal." Connect your meter to as close as you can to the VR ignition terminal. This would be the "key" side of the ballast resistor, where the two wires are jumpered together if you have a 4 terminal ballast. Otherwise, probe from there to ground and find the HIGHest reading. Then leave one probe of your meter hooked there

Then, stab your remaining meter probe into the POSitive battery post. You should read a very low reading the lower the better. ANY reading here is ADDED to the charging voltage set by the voltage regulator. If your read more than say, .3V (3/10 of one volt) you need to find the problem

They are in no particular order: the bulkhead connector terminals, the ignitions switch connector, the switch itself, and on newer cars, THE WHITE underhood ignition harness connector.

One way "around" thsi is to cut (electrically) the blue "ignition run" (ign1) wire coming out of the bulkhead and into the engine bay. Use the bulkhead connector end to activate a relay, and feed the relay contacts from the start relay "big stud." Connect the underhood end of the cut blue wire to the switched side of the relay contacts. This will provide a good direct path from the VR to the battery