PDA

View Full Version : Where to put the ground.



doughairfield
05-01-2011, 11:02 AM
I'm changing over to a pertronix Flamethrower distributor this weekend on my positive ground TR4. The instructions indicate I need to have one wire on the new distributor connected to the negative post on the coil and the other wire on the distributor needs to goto the ignition switch.

Currently with the old distributor in place, I have the positive post on the coil going to the ignition switch and the negative post on the coil goes to the HT lead on the distributor.

Once I remove the wire going to the positive post of the coil and connect that to the new distributor, what's a good place to ground the positive post of the coil to?

Any other gotchas or tips on putting the new distributor in?

Twosheds
05-01-2011, 11:21 AM
I'm changing over to a pertronix Flamethrower distributor this weekend on my positive ground TR4. The instructions indicate I need to have one wire on the new distributor connected to the negative post on the coil and the other wire on the distributor needs to goto the ignition switch.

Not that it matters much, but this is like a negative-earth car.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Currently with the old distributor in place, I have the positive post on the coil going to the ignition switch and the negative post on the coil goes to the HT lead on the distributor. [/QUOTE]

Not that it matters much, but this is like a negative earth car.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Once I remove the wire going to the positive post of the coil and connect that to the new distributor, what's a good place to ground the positive post of the coil to? [/QUOTE]

It goes to the ignition switch.

doughairfield
05-01-2011, 11:34 AM
Googling negative-earth car........

Ok, it's a little more clear now. So if I understand this correctly, the switch is providing the ground to the coil when it's put in the on position, completes the circuit, and the car starts. Right?

So, since I already have the positive post of the coil wired to the switch, can connect the wire from the new flamethrower distributor to the positive post on the coil as well? In the instructions they have that wire going directly to the switch and the positive post of the coil going to ground. Is this correct/ok?

Twosheds
05-01-2011, 12:41 PM
Don't pay any attention to me!

I was thinking about a stock distributor. I don't know about a Pertronix distributor! Sorry!

But I do know this: (I think)
the switch is providing the ground to the coil when it's put in the on position, completes the circuit, and the car starts. Right?

The switch is not providing a ground, it is providing "hot" to the coil. "Hot" just means the ungrounded or unearthed (sounds creepy) polarity.

Hopefully, The Randall will straighten me out, as usual!

TR3driver
05-01-2011, 01:36 PM
The Pertronix works differently, when the positive ground version is installed in a positive-ground car. You need to wire it exactly as the Pertronix instructions state, ignoring how similar or different it may be to other installations.

My suggestion would be to make up a new, short ground wire for the coil, with one terminal to match the positive (or CB) terminal on the coil and a ring terminal on the other end to go under one of the coil mounting bolts. Then connect the original harness wire to the distributor wire that is supposed to go to the switch (which I am guessing is black); and the other distributor wire to the negative (or SW) terminal of the coil.

The coil doesn't really "care" whether the hot or ground side is switched to cause a spark, it is just usually simpler to switch the ground side. But for whatever reason, Pertronix prefers to switch the hot side for positive ground setups. I don't know why that is, but I would guess that their module was designed to use a silicon NPN switching transistor, which at one time was the clearly superior choice.

doughairfield
05-01-2011, 02:38 PM
OK, thanks Randall. I'll let you know how it goes.

doughairfield
05-01-2011, 09:33 PM
Excellent advice Randall, runs like a scalded dog now.

Thanks!!!