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TR7 coil and Accuspark confusion


Colin Lindsay
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I'm on a roll with the TR7 and am finishing off the engine bay, but the coil / ignition circuit is causing confusion. I removed the points and fitted electronic Accuspark ignition. The Accuspark has two wires, one red, one black. I've spent the last while trying to make sense of the wiring circuit but nothing that I have matches any of the manuals.

My coil has two wires, white / brown(?) and white. It could be white and slate but it's from the coil earth. The other is white and yellow.

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Any of the wiring diagrams I've consulted, Haynes included, talk of 6v coils, ballast cables, cables, white and slate, white and yellow, and three or possibly four wires from the coil to a distributor pack. 

So: how do I tell if it's a ballasted system? (probably a ballast loom, I can't see any ceramic block)

I think, but it was 18 months ago, that the original points emerged to a connector down by the bellhousing - just one wire, and I think this connector is the same black and white that originally came from the points - anyone know? 

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without  a diagram i would say white slate is the ballasted feed from the ign switch  the white /yellow is the 12v boost  from the starter  solenoid both go to the +ve coil terminal the wire to the dizzy  -ve  is from the accuspark ( probably the black

i presume the red is a 12v feed to power the accuspark 

if its balasted the coil is 1.5ohms   checking the ballast wire voltage can give you 12v readings depends if the leccy unit ' points'  are open or closed

is that any help 

Pete

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I've just checked a few online posts / videos elsewhere and is it as simple as red to positive on the coil, black to negative on coil? 

It was bought direct from Accuspark for the TR7 so I'm assuming - hoping - they know it's ballasted if that makes any difference at all but they say: 

The Accu Spark electronic ignition is a complete unit that completely replaces points and condenser (requires no other parts ) . There is no wiring it only requires only 2 simple connections. Red to positive on coil ,black to negative on coil . Once fitted the points can be refitted at any time. 

I was perhaps trying to be too clever and connect it to the existing wiring half way along the loom but that's where the confusion arose; however quotes like the one below from another TR forum are also causing confusion:

"You also has to add a separate wire from the distributor and connect to wiring under the dash near steering column. I was able to do this so completely reversible if required. The extra wire is because our ballast resister is within the wiring not attached to the side of the engine "

The above, I assume, is because the 6v system will result in a weaker spark. Others are saying to disconnect the yellow and white wire at both ends and run a 12v coil. White / slate is apparently the tacho drive. So what was simple to start has now caused a lot of headscratching.
 

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a 6v 1.5ohm coil produces the same HT as a 12v 3 ohm coil what you should not not do is mix and un match the two systems

a 12v supply to a  ballast  1.5 ohm 6v coil doubles the amps and the HT blows rotors and  more 

 a 6v feed to a 12v 3 ohm coil halves the current and the HT so points last for ever but you get a very weedy HT spark 

and being a dinosaur i had not thought about the elec rev counter impulse wire  

Pete

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22 minutes ago, Pete Lewis said:

a 6v 1.5ohm coil produces the same HT as a 12v 3 ohm coil what you should not not do is mix and un match the two systems

a 12v supply to a  ballast  1.5 ohm 6v coil doubles the amps and the HT blows rotors and  more 

 a 6v feed to a 12v 3 ohm coil halves the current and the HT so points last for ever but you get a very weedy HT spark 

and being a dinosaur i had not thought about the elec rev counter impulse wire  

Pete

Ok so now I'm completely confused... :)

When you say a weedy spark is that on startup, or all the time the car is running? 

If I keep the current coil as is, and simply connect the red and black wires to the coil, will the car start and run with no damage to anything?

52 minutes ago, thescrapman said:

It will run on 6v, just not as well.

change to a 12v coil, and modify wiring, or just run the red wire to a 12v ignition switched feed.

Now: if I change to a 12v coil, and simply unplug and insulate the white / yellow ballast wire while connecting the red and black to the coil, what happens? (Where does the other end of it go, by the way?)

 

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yes weedy spark running  good spark when white yellow gives is a 12v shot when cranking.

in general most leccy units run on 6 to 18v as a range , if the battery is poor and cold then the 6 v can drop and the unit plays up a bit 

and yes connect as you say and it should do what it says on the label, re time the ignition as the pick up and old points are not set to work in the same position so timing reset is a must .

Pete

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