Coil polarity

jjbubaboy
jjbubaboy Senior Contributor
edited November -1 in HUDSON
Hey,
So, I have the vintage style Autolite coil that has one terminal on the bottom and one on the top (besides dist wire terminal.) Since the wire from the keyswitch goes to the coil bottom I presume that is the negative side of the coil.
Is this correct?
I am planning on putting a pertronix in it and dont want to hook it up wrong.
Thanks,
Jeff

Comments

  • Marconi
    Marconi Senior Contributor
    You've got it backwards, Jeff. The battery terminal that's grounded is the terminal of the coil that goes to the points. So in your case pos goes to the ign switch and neg goes to the dist.
  • jjbubaboy
    jjbubaboy Senior Contributor
    So that means negative power goes to positive on the coil??
    And the positive ground is on the negative side?
    The coil is installed upside down on the firewall so the plug wire to the distributor and the ground wire both come from the top which is pointing down.
    Jeff
  • [Deleted User]
    [Deleted User]
    If he is still Hudson 6 volts, positive is ground and distributor wire goes to the positive side of the coil. Negative is from the key to negative side of coil. If 12 volts then you are correct, positive distributor to positive side of coil. Walt.
  • jjbubaboy
    jjbubaboy Senior Contributor
    Hey Walt,
    Yes I am still 6v pos ground system. Guess I am just confused as to how pos and neg are hooked up to the coil.
    Thanks,
    Jeff
  • Park_W
    Park_W Senior Contributor
    Jeff, did you really mean still confused? If you have that original style coil and you're still 6v positive ground, just ignore what's pos and neg and hook it up as originally done. Wire from ignition switch goes to the terminal on the bottom center of the coil; the other terminal on the coil goes to the distributor.

    As Walt said, the center terminal on the coil is the negative one; the other terminal is positive. The distributor points ground the coil when they close, and ground on the car is positive. Having the polarity correct is important. A Delco training manual I have says you lose about 15% of spark voltage if you have it wrong.
  • jjbubaboy
    jjbubaboy Senior Contributor
    Thanks Park, Walt, and Marconi!
    I do know how it is wired up, I just didnt want to mix up the coil positive and negative when hooking up the pertronix ignition. No where on the coil is it marked + or - and the instructions are set up to wire the pertronix by + and -.

    Park, I do remember doing that on a old Chev I had and like you said it did run but not so good! Took a while to figure that one out. But in this case it might burn the electronic module out and I dont want to do that.
    Jeff
  • Park_W
    Park_W Senior Contributor

    Jeff, the most dramatic demonstration I ever saw of the weakened spark with incorrect polarity was back in 1955 ... a buddy and I put a '53 Caddy engine in his '51 Hornet coupe, and all went well in the transplant except that when it was ready for the road, the darned thing wouldn't go over about 30 mph. Drove us nuts trying to figure what the problem was (kind of embarrassing, too, as we were both instructors in the Air Force's aircraft electrician course and "moonlighter mechanics" in a local garage). Finally saw that the coil polarity was wrong, but figured "OK, we'll change it, but that couldn't possibly be the problem." Wrongo !!! The beast ran beautifully. Apparently that fairly high compression Caddy with still a 6v system needed all the spark it could get, so losing 15% was a major problem, as we found out.
  • jjbubaboy
    jjbubaboy Senior Contributor
    WOW! Now thats a cool install and very clean looking too.
    Thats about what we figured out as well!

    Got the Pertronix installed and put the dizzy back in. Wired it up, turned on the key and hit the button. VROOOM she started right up! Will check the timing and they go for a drive and see how she runs in the next couple days.
    Thanks again for all the info all.
    Jeff
  • Park_W
    Park_W Senior Contributor
    Jeff, re the Caddy installation photo, look at the rear part of the exhaust manifold, and observe how the shallow bend inward matches up with the big angle brace from firewall down to the frame. Looks like the Caddy was made to go in there! Based on how well this worked, I put a '55 Olds engine in my Hornet convertible about a year later (Fall of '56) when the 80,000 mile six-banger need a rebuild. Made a nice combo.
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