Ignition coil question

[Edgecrusher]

So I came here to clear up something I haven't been able to wrap my head around pertaining to the operation of an old two wire ignition coil.

I have an old VW baja and I recently installed a crank fired ignition and computer on it. It still has the stock distributor and coil but obviously no coil wires are present, just the wires for the newly installed system. Temporarily, I have the coil and dizzy powered so that I can get the tach signal for the Tachometer and see my RPMs. Again, I have no high tension lead coming off the coil.
So effectively, I have the primary side of the coil energized but there's no circuit on the secondary.

Will this damage the coil? Will it heat up or will the potential find a way to bridge the very big gap between the HTL plug-in and ground? Or is the resistance so great in this case that there will be no potential and no current flow?

 

[Diver300]

It could damage the coil. It would be better to short out the high tension connection.
Alternatively, just use a resistor.

 

[danadak]

The much higher output V that develops could create carbon tracks
from arcing, and depending on plastic used in HV output housing
could lead to permanent problems. Same is true internal to coil.

Regards, Dana.

 

[crutschow]

An ignition coil can break down internally if the output is open circuit.
Connect it to ground.

 

[Lightium]

The voltage tries to find the path of least resistance, and so the secondary will break inside the transformer.

 

[crutschow]

The voltage tries to find the path of lease resistance, and so the secondary will break inside the transformer.

It's not the resistance, but the voltage breakdown value of the insulation from the high voltage.

 

[aliarifat794]

Without the secondary circuit completed, the energy stored in the coil during each cycle has nowhere to dissipate properly. This can cause the coil to overheat and lead to insulation breakdown and coil failure.