1970 W108 M130.980 Points to Hot-Spark Conversion

[cwb0711]

Hello all,

New to the group, but not to MB. I'd appreciate if other could share their experience with converting the TI M130 from points to electronic ignition, especially Hot Spark. The TI Module is designed to drop the voltage at coil + to about 3V with the OE coil; with the Hot Spark 1.5 Ohm coil this results in 0.7V at coil +, and the module requires normal (12V) voltage. Has anyone removed the TI Module and associated ballast resistors, or simply bridged (run a wire) from IGN 12V to coil+? I haven't done this yet, but it seems fairly straightforward and would appear to render some hardware as "spare parts". Hot Spark says run a 12V wire from IGN to coil +, but has no specifics for this set up.

Thanks

[Frank Reiner]

With the original MB transistorized (TI) switchgear, current control is accomplished via coil resistance plus external resistance (~.4+1ohm). When the points are closed, the current will be approx. 8.5-9A. Avg. current with engine running approx. 3-4A.

Aftermarket systems will have about the same total primary circuit resistance, however, external resistors are not used; the resistance is internal to the coil. Peak and average current will be about the same, although there may be a a current limiting circuit in the aftermarket system.
When installing an aftermarket system, follow their instructions.