[wslade2]

Alot of interesting information here, have been reading and absorbing very interesting stuff.

I did find in the maintenance manual that the purpose of the restart switch is for when the alternators drop out due to high electrical load such as use of flaps motor (see attached photo of page out of maintenance manual for my E model). Apparently the older systems (voltage regulators) would drop offline with heavy load. Maybe we don't experience/expect that as much now with more modern electricals, lower draw avionics, better charging gear.

I can not find in my manual any specs on maintenance of the system.

Now I am probably going to do something I will regret as I am sure there is someone more knowledgeable than me. But I will stick my neck out here.

Thinking about the original problem, there is a low voltage at the field connection of the alternator when the restart button is pushed, 0.3v and 0.6V. Something in the back of my head, that I may have read a long time ago, says it doesn't take much juice to restart an automotive style alternator field. Witness the battery pack of 2 D cells (3V) or 4 C cells (6V). That said: thinking back to college physics, decades ago (gulp), V (volts)=I(current) x R(resistance). So we have a circuit with 4 cells and a resistor with 12 ohms. Best I can find, looks like healthy "C" cells are capable of 1 amp a piece unbridled. So that means when the button is pressed 4 amps max can come out of the box. Suppose the cells are at least a little dated. Maybe assume 0.5 amps max output a piece, or 2 amps when the button is pushed with a somewhat dated contents in the battery box. The voltage drop across a resistor will be subject to the V=IR rule. So assuming 2 amps of current and 12 ohms of resistor, 2 x 12 = 24 volts drop across the resistor. Subtract 24 volts resistor drop from the 4 "C" cells voltage of 4x1.5 = 6 volts and an output of 0.3 to 0.6 volts at the alternator field starts to sound pretty good. This gets to MSHAC's question of what should the voltage at the alternator field terminal be when that switch is pushed. And maybe the answer is pretty low.

Also, the issue to excite the alternator may not be so much voltage from the restart circuit, but current. Current, movement of electrons, creates the field that the armature spins in to generate electricity. When the button is pushed, it's not so much how much voltage is in the field but how much current is going through it. Again, V=IR or V/R=I. We have 6 volts of "C" cells and 12 ohms of resistor: 6 divided by 12 = 0.5 or 1/2 amp. My reading, 1/10 of an amp is enough to excite an automotive style alternator.

I will not be offended if I get quickly dispatched on my discussion by anyone more knowledgeable. Just sticking it out there. Maybe the voltage stats detected are the norm.

Perhaps the next test is not a voltage test of various wiring junctures but an ammeter test of the alternator restart circuit. See how much or if any current flowing through when button pressed. Also, another next step might be a test of the system switches per the procedure outlined by others here to see how the system works. Or was dysfunction on a test what started the dive into probing the circuit?

see attached