620 coil voltage

Youre correct assuming certain things such as:

There ought to be around 6 volts on the coil (In a 12 volt externally ballasted system) IFFFFF FFFFF all is wired correct,,,,, ,and the coils primary is good and continuous,,,,, ,,and MOST IMPORTANTLY,,,,, ,if the points are good and are FULLY CLOSED,,,,, and the points and distributor are grounded to the frame. (Inspect the poinst for closure and condition and their wiring including to the distributors pass through terminal)

If the points are good and closed and the coil primary is continuous, if you place a test lamp on the coils low (to distributor) terminal it should NOT glow when the points are closed (if they are good) or the ignition is OFF !!!!

If the points were bad or open (but theyre usually closed as its hard to stop pistons at TDC) or if the coils primary were open or the distributor not grounded, theres no current flow through the ballast to create a voltage drop across it and you would read batetry voltage on the coil buttttt ttt then she wouldnt spark either !!!!! !!!!!

You might wanna dead ground the coils low output (to distributor) terminal and then measure voltage on the coils other high input terminal ????? ? When you do that you are duplicating what should happen if a good set of points are fully closed, wired correct, and they and the distributor are grounded, and the coils primary is good and continuous.

If youre NOT dropping volate across a good n proper wired 2.5 ohms ballast resistor it must not be conducting any current

NOTE Youre also correct in that wire up from the starter switch should be hot ONLY while cranking. HOWEVER if it were bad or miswired such that it always has hot 12 volts, that would create 12 volts on BOTH sides of the ballast and the coils input,,,,, ,,,,try unhooking it n see what happens????? ?? BUTTTTT if it were always hot the coil voltage would remain hot and the coil get hot even if the ignition switch were turned OFF but if the coil is wired correct the ignition switches MAG terminal (when OFF) ought to be premanently grounding the poinst so theres no spark.

Lemme knowwwww www

John T

A litte more data. There is no voltage coming from the starter when not engaged. I have 12V coming from the switch to one side of the resistor. I disconnected the wire from the other side of the resistor. I have 12V to ground from each side of the resistor, even the side with nothing attached to it. The resistor still reads 2.5 ohms. The 12V to the coil is coming from the resistor. I don't know how it can read 2.5 ohms of resistance and have no voltage drop through it. Is my resistor bad?

My 620 is neg ground. I have the negative terminal of the coil connected to the distributor. Is that how it should be? I think so based on another thread here. Is the coil just a step-up transformer? Which is the primary and which is the secondary? Thanks for your time.

In order for the resistor to drop 6 volts as its supposed to, its low side must be wired to the coil and then the coil must be good with its low side wired to the distributor and the points must be good and be closed. My original posts pretty well described all that no sense repeating it all again.

Its all gotta be wired up and working and the points closed before youre gonna see 6 volts on the coil.

YES if at Neg ground the coils lil + gets voltage from the ballast resistor and its lil - wires to the distributor.

YES it functions sort of like a step up transformer

The coils low voltage primary is between its lil + and - terminals while its high voltage secondary is out the top center high voltage tower.

John T

Yeah you're right about no voltage drop without a circuit. Been too long since physics and circuits classes. If you don't use it it gets put on a dark shelf somewhere and is hard to find again. I will go back over your previous post and get a proper voltage measurement at the coil. Thanks again.