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How to Test a 123ignition

Bench Testing a 123 Ignition

Testing the Switched Model
Using a regulated power source like a 12v or 6v transformer you would connect the red 123 wire to the +ve on the transformer.
The -ve of the transformer would need to connect to the body of the 123. This is ground.
While the black from the 123 (if used) could have a light and also connects to the +ve. This would give a visual of the spark.
Testing the TUNE Models it is slightly different.
Red goes to the +ve on the 12v or 6v transformer.
The Blue connects to the -ve of the transformer. Which is ground.
While the black from the 123 (if used) could have a light and also connects to the +ve. Simulating the generated spark.
Testing the unit in the Car!
Basically in this diagram you are replacing the coil with the light
Some Suggestions to check

-the +12V of the red wire is not connected on the coil +12V and this point gets interrupted by the ignition key when the starter is engaged

-bad connections in the wires and or high resistance in the ignition key lock*)

-bad grounding of the 123 unit *) in the engine block (I suggest using the M6 hole to attach an extra ground wire to the block)

-the spring loaded center graphite contact has fallen out of the distributor cap or is stuck in its hole and its spring does not push the pin against the rotor arm

-spark-plug leads or and or coil that with not enough isolation *)


*) Due to automatic coil current control and faster charge of the coil, peak currents in the low voltage circuit are higher and resistances can cause problems. The higher spark voltages in the HT circuit require better isolation in the HT leads and coil.