charging problem

When you make the test as I suggested, you do not run the starter, is that what you are trying to do?

The battery cannot possible drop much during that short test, or it would never crank the engine at all.

But your running test "actually" shows what we want. You have the DIFFERENCE between 14.8 and 14.2. The 14.2 shows that the regulator is trying to regulate "at that" voltage. That is, it is looping to maintain it's "sense" point (the regulator IGN terminal) at 14.2. The fact that the battery is running HIGHER means that the voltage the regulator "sees" from the battery is LOW.

In other words you have a .6 voltage drop between battery........through all the harness and connectors and the switch.........to the regulator.

An "easy" way to "fix" this is to install a relay to feed the ignition / regulator