Duraspark II question

Got the 5.0 roller motor in my truck. I hooked up the Duraspark II parts but found something that seemed very odd. The voltage drops when I connect the module to the power wire. I'm using the wire that provided 12v to the original 69 coil. When I connect the new coil the voaltage stays at 12v, add the module power wire it drops to 5.75 to 6v remove the wire it goes back up. I pulled the power from the switch side of the starter soleniod, same thing. Power direct from the battery stays at 12v. With the low voaltage the truck has a bad stumble at mid range, power from the battery clears it up. I don't mind running a new wire, adding a switch under the dash etc. So is this normal voaltage rates? Does this mean the module is bad or going bad? Sorry about the length of this post I just wanted to try and cover all the bases. Help...........Rick

When I put one in my 64 I had the same problem with the original resistance wire. The added draw of the new parts drags the voltage down too much. I removed the resistance wire [under the dash on mine] and used standard wire. I then used a mopar style ceramic resister. I ended up putting the ignition on a relay to get it off the ignition switch. That should fix it.

So I not going crazy! Thanks for the info, the relay hook up sounds good to me. Thanks again........Rick

He's right, the original wire to the coil is a resistance wire that only let's 6V pass...