Re: 1969 Engine Wiring Harness Replacement - will not fire
Floyd, Yes at Crank the feed voltage resistor wire is bypassed and supplies full Bat+ directly to PU coil and TI circuits. After Crank and engine running, the circuit voltage reverts back to raw IGN power. Since the alternator is now charging and potentially 13-14 volts, the resistor wire in the feed circuit takes over to reduce voltage to both the PU and the TI Module. The feed resistor wire is around 0.7 ohms. I've never measured the running voltage at the TI module or PU inputs, but probably in the 12.5v range as a guestimate.
TI is more thought of as a electronic high speed "switch", i.e. transistors, to trigger the primary Ign Coil+, and Coil- is fixed directly to ground(66-71 TI).
Note on 64-65 TI, Coil- is actually grounded via the resistor wire, and coil+ directly from TI output transistor circuit, not through a resistor. Explanation for this change in configuration? I have no clue.
Rich
PS - a few years ago I did some TI bench testing to diagnose and old Delco circuit. Some waveforms of the "switches" included. HERE
Full thread HERE if bored.
Floyd, Yes at Crank the feed voltage resistor wire is bypassed and supplies full Bat+ directly to PU coil and TI circuits. After Crank and engine running, the circuit voltage reverts back to raw IGN power. Since the alternator is now charging and potentially 13-14 volts, the resistor wire in the feed circuit takes over to reduce voltage to both the PU and the TI Module. The feed resistor wire is around 0.7 ohms. I've never measured the running voltage at the TI module or PU inputs, but probably in the 12.5v range as a guestimate.
TI is more thought of as a electronic high speed "switch", i.e. transistors, to trigger the primary Ign Coil+, and Coil- is fixed directly to ground(66-71 TI).
Note on 64-65 TI, Coil- is actually grounded via the resistor wire, and coil+ directly from TI output transistor circuit, not through a resistor. Explanation for this change in configuration? I have no clue.
Rich
PS - a few years ago I did some TI bench testing to diagnose and old Delco circuit. Some waveforms of the "switches" included. HERE
Full thread HERE if bored.

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