No power to ignition coil

[tr1cky]

Originally Posted by marcedesbenz

Are you using stock coil? If so then I think you will still need the ballast resistor, I purchased a new coil that has internal resistor. Bypass the ignition module completely for simplicity, just leave it in place in case anyone later is insane enough to put points back in. The wiring of my pertronix was really easy. there are schematics floating around these forums, but 12 volt hot to coil at all times ( when key on), black from hot spark to coil negative, nothing else should be on the coil negative ( thats what fires ). Red from hotspark to any positive 12v ignition source. I put mine straight to the same positive for the coil. Its that simple. I am going by the pertronix, the hot spark may be different but should be same logic.

Rock on! Per the hot-spark instructions two wires aside from wires that are already on the coil are the red to the + and the black to the -.

[marcedesbenz]

The mercedes ignition system is the reverse of every other system around. Make sure there is no ground on the coil except the wire from the hot-spark module. Originally the coil had a ground all the times and the positive was used for firing.

[tr1cky]

Originally Posted by marcedesbenz

The mercedes ignition system is the reverse of every other system around. Make sure there is no ground on the coil except the wire from the hot-spark module. Originally the coil had a ground all the times and the positive was used for firing.

Thanks for your thoughts and comments. I confirmed setup as you described. Still no spark.

Dang.

[ctaylor738]

I got lost in all the twists and turns. You need 12V from the ignition switch to the + side of the coil. The easiest way to do this is to run a wire from the 12V feed to the first resistor after the ignition switch to the + side of the coil.

If you did this and you don't have spark, you may need a higher resistance coil.

[tr1cky]

Thanks all.

I had been relying on power from
one of the existing wires. I went right to a 12v power source and solved the problem.

Ugh. 40 year old electrical gremlins are the devil's work. Now the car has an extremely healthy spark. Now back to the carb.

The hot-spark brightened up the spark like day and night from the original setup.

[ctaylor738]

Nice work.

One caution - units like Pertronix can fry themselves very quickly if the ignition is left on without the engine turning. So the suggestion is to put a switch in-line on the wire to the coil so you can cut the power if you work on the horn or wipers, etc and need to have the ignition on.

[tr1cky]

Originally Posted by ctaylor738

Nice work.

One caution - units like Pertronix can fry themselves very quickly if the ignition is left on without the engine turning. So the suggestion is to put a switch in-line on the wire to the coil so you can cut the power if you work on the horn or wipers, etc and need to have the ignition on.

Great thoughts and thanks for your advice on this. I've heard it from others before and will consider this.