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Bosch HEC716 and 123ign

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123 experts: 
I've google'd/searched without success about using a Bosch HEC716 coil (or equiv) with a 123ign dizzy.

Reason I ask - I've had some coil issues recently and have a HEC 716 lying around that I got from a mate. We used to run them in our Liberty RS Turbo when the OEM ones cooked. 

Bosch red or blue coils are near impossible to get at the moment here in Australia. 

123 recommends above minimum 1ohm across the primary - the HEC716 I've got at home is 0.8 ohm, 8.7k on the secondary 

What is the risk with running a lower resistance coil - burning the cap & rotor? 

Thank you


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On their site, they recommend the Bosch blue coil for four cylinder engines and those have 3 ohms of resistance built in. 


Perhaps, you could use an external resistor to increase resistance and run the one you have.




The ceramic resistors that came on pre-'74 cars might work. BMW part # 12131353362


@John76 just posted this drawing an hour ago, showing how to install an external resistor.



What year is your car? If it's got rectangular tail lights, it might still have the resistor wire that fed the original coil.


Or, simply switch brands and buy a coil with 1 ohm + resistance, as Furry suggests.


I wouldn't go below one ohm, based on their recommendations.



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20 minutes ago, Furry Camel said:

What's more expensive? A new 123 distributor or a >1 ohm coil? Is the risk worth it for a $50 coil? (Because warranty does not cover damage from using a coil it specifically says not to use.)

It's more for curiosity than anything - that's why I'm asking. I've bought 2 new oil filled coils in 2 months, first one last 4 weeks. I know my wiring is correct as I've had this configuration for years. 

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On 1/21/2024 at 8:32 PM, '76mintgrün'02 said:

On their site, they recommend the Bosch blue coil for four cylinder engines and those have 3 ohms of resistance built in. 


I'm now using a Bosch red coil on my 02 with blessing from the folks at 123. It did make a butt dyno measured difference from the blue coil it replaced especially at upper RPMs. 

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The blue coil with resistance wires and 5k rotor and R plugs is a fail....


...but I've also blown up electronic ignitions by using a too- low resistance (impedance)

primary coil.


So ask the 123Squad if it'd be ok to run .85 ohms with a .2 ohm resistor. 




  • Like 1

"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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