GM Coil and Module Help Required
I think you are incorrect about a couple things here
Quite possibly.... :) i do tend to just shout out what i think...
but there is something in it as far as i can tell, but my view or what it is is potentially wrong... Alternator is connected to battery +. which is connected to the diode setup which is connected to the 3 phase coils in the case. The action of a quickly changeing magentic field made by the rotor produces the voltage in the case windings to charge the battery and run the car...
Car Running and the field is at maxiumum, and the alternator is chargeing at 14.? volts, you might have 30 amps flowing in the case windings or at least out of the stud to the car/battery
stall it. the field is still ON, the field coil in the rotor is seeing 5 volts from the regulator becasue the battery just started the car and is flat-ish, and the ignition switch is in RUN.
But the rotation driving the production of 3 phase in the case windings HALTS abruptly. Big immediate change in interaction of field around rotor with the wireing in the coils in the case, you end up going from constantly varying AC generation north south north south across each winding as each segement of the rotor passes, to a stock-still North Souh across the coils that doesn't move, becasue the engine went from 1500 rpm to 0 in 1/4 of a turn.
field/rotor current increses (its now stopped, no impedence to flow) and case widing current drops like a stone.
What was a continually and fast variation in magnetic field, is now stock still. A big change in field. That 30 amps in the case windings just stopped abruptly as well. 30 amp to zero in a split second, also creates a magnetic pulse of considerable magnitude and how it combines with the one caused by just stopping the rotor i dunno.
what comes out or goes into to the battery + to or from the car, in that fraction of a second when you stall is open to debate. battery + is however connected directly via the igntion switch and then to the coil and module + and the other end of everything is earthed.
so what did the coil see and what did the module see when the voltage at battery + did something wierd. potentially big-er volts in a positive or negative way...... even if just 20 or 30 its out of the general tollernace for car electronics.
Yes its a half baked idea, its not well formed BUT it comes from:--
I had a situation a few years back, a massive gradient on the drive, if the fuel in the tank was low i couldn't start the car, nose down, tail up. I couldn't then open the garage door to get to the fuel can.... i could drive in but getting it back out again the next day was a problem, you needed a decent fuel level to park nose down on the drive, you could park in the garage below no problem with an empty ish tank. car lived in a garage under the house, no starting choke and ostensibly 6 carburetors 3x dcoe that don't work well when not warmed up. and its a manual
steepness gearing and fuel issues
in a hurry, without 5 minutes warm up, it was easy to stall it halfway up the drive, the kinda stall that is like a punch to the head, that you just can't manage to cause with a fluid coupled auto.
At the time i had 2.92: ratio rear end, an obnoxiously heavy clutch and a less than easy reverse gear ratio.
I did 2 or 3 modules this way until i moved house...
and of course you never knew if it was fuel level or module. feel my pain.
So trip to get can of fuel, which on occaions resulted in no change, was followed by module replacement...and suddnely all is well again.
If this happend in random places i'd suspect low quility modules... its something else.... but it all happend in the exact same spot with the same scenario on days when you least needed it to happen.
and i didn't really form this theory until i got talking to some of my mates about it, who run in the UK superstock series... i.e more $$$ invested in their cars than i will ever manage.
General consensus was that the emergency ON-OF switches they had in the tail of their cars came in a number of types appropriate for the electrical complexity of the car. For a points car with no ecu type stuff its an ON OFF switch. battery and alternator feed OFF. it isn't a complex thing. 3 or 4 stud mounted fat wires and job done battery in boot fuel pumps in or under boot, so near by.
but if you want to do it right you have a multi pole multi throw switch for different circuits in the car, and the throw of each pole is offset slightly to avoid a situation similar to above, where the unexpected removal of power casues bad stuff to happen
more studs and connections.
igntion circuitry off first, then fuel system (an electric motor) next, then battery and alternator disconnect, from what i remember, i might have it the wrong way.
All in a 1/4 turn of the big red switch.
Seemingly do it the other way with the engine running at more than idle and you might take out your ECU and other electronics. (we are talking a track emergency, fire suited man swicthes off car because you can't, unconscious or thottle jamed, upside down etc and a few of them had been upside down etc in the past)
Then they all had a spirted conversation, some guys insited this was the case, alternator and coil could kill your expensive stuff....there were doubters who said it was all BS... you are all daft just keep it simple etc.
but the guys running expensive electronic equipment sided one way and the guys running basic stuff didn't seem to care, its hard to break a dual point distributor.
but maybe this is why their MSD6 boxes keep dieing.... ??
since those days, ive included a zener diode to clamp the reverse voltage the module can see i've not had a problem. but i also don't have the facilties like a stupid steep drive to promote a stall, under medium rpm and medium torque on a cold engine. Better gear ratio torsen diff better ignition coil different 4 speed and a better tune.
the issue could have been driven by the ON OFF ON at the key to restart the car...when preceeded by a stall....i dunno.
I'll admit one mans experience doesn't make for a thing...but in my world something is going on, and by coincidence i found a small group of guys who also think its a thing....
it might not be and they have more to damage than I do. A more expensive emergecy cut out might be cheap insurance, and that could be drving their view.
Bewy yes i have got my module and pickup wires mixed up. some pontiacs spin the other way....
Dave