m010702

I've just put in a new engine wiring harness. According to the MSD paperwork, one of the connections must meet with the original coil (+) wire. The new harness has a coil lead that consists of a black wire and a yellow covered wire bound at the end with a simple spade connector (meant to go on a stock coil). Of note, the paired wires have a note on them instructing NOT to separate; something about a resistor I think. Can I simply plug the MSD lead on to these wires. Assuming they are switched 12V. Thanks.

0Willcox Corvette

If I remember correctly, you are not supposed to hook the MSD up to a resistance wire. The speckled wire you speak of is a resistance wire.

I think it requires direct 12 volts. Check your schematic and see if I right. Someone else will post after this bump. I'll try to dig up the schematic and look at it. Is the box the 6AL.

Willcox

TimAT

One of those paired wires is the resistor wire with the key on. The other one comes from the starter and is 12+ only when the starter is engaged.

m010702

its the 6A. looking at the diagram there is a lead that has to be hooked to the battery (12V) that is 12 gauge wire. Another lead, smaller (maybe 16 gauge) is supposed to go to the original positive coil hookup. Wilcox, any help would be awesome! if its not that dual wire hookup, what can it be??

Dantana

Heavy red and black go to the battery, this is key. You should have 1 switched wire and an orange and black wire for the coil. The distributor connects to the coil using a 9mm (or so) booted wire. All that remains is hooking up the distributor using either the supplied connector out the other side of the box (purple/green) or the individual wires. You're in business!

-at least I hope you're in business, I did that from memory...

baxsom

are you using the 6AL
instructions on page 5 say to bypass the resistor wire

TimAT

Run an ignition box on low voltage and you get to replace it soon. The electronics are fairly rugged, but low voltage = high current and the smoke will leak out.

m010702

all,
sorry to keep going into the weeds on this one. remember i'm a novice who has people on all sides giving different "technical" opinions. A guy today was over at the car...used to own a '71....said that he thinks the yellow wire (of the yellow and black combo designed to go to the coil) only receives power when the key is in the start pos'n. Later another fellow said that he thinks that the yellow line is constant 12v whenever the key is in the on position. "IF" the yellow line is switched 12v (constant in the "on" key pos'n) I plan on removing the black resistor wire, and hook this into the MSD. Is this correct? If this isn't constant 12V, from which location do you all recommend tapping this power. Hopefully my questions are clear; will be checking this thread a good bit as I am hoping to finish wiring this weekend and fire the car up soon for the first time in 2.5 years...good times await!

TimAT

The black and yellow pair- one of them runs from the ignition switch to the + side of the coil that one is the resistance wire built into the harness I don't have a 71 diagram, but 69 shows it as black with a red/white stripe (maybe other way around can't tell). And my 74 diagram shows the black is from the switch and the yellow from the solenoid too. So that leaves the yellow wire. that runs from the starter solenoid to the coil, and is hot (12v+) ONLY when the key is in "START". (well, it does have power when the key is on, but just because it's hooked to the black wire at the coil)

In light of that, you need to get a switched full +12v to the MSD. I suggest running a new wire from the fuse block. If you go to the block there will be an empty connector that's marked "IGN" and one marked "BAT". "BAT" is hot all the time. Not the place for an ignition switch. Go to the "IGN" and connect it there. Check it wih a test light to double check that it's hot with the key on and not hot all the time. (Never hurts to verify, after all, who knows what's happened in the last 30+ years!)

Found a link- check your PM box

Dantana

Do you have a multimeter? You can just check the wires to see which is hot and which is switched.