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Old 06-17-2016, 09:29 PM   #1
Bassman/NZ
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Default Burning points??

My crab dissy was built by Bubbas and has done about 1,500 miles. Because it suddenly refused to start, I took it off the engine and found the right-hand pair (as viewed from the front of the car)of points were burnt and badly pitted. Now I know that Jim uses quality points, so I'm suspecting something has caused this.
12v, neg earth system, running to a ceramic ballast resistor, running to neg side of a 12v Bosch coil, pos side of coil to condenser. Do I have the coil the right way round? Should the ballast resistor perhaps be after the coil? What should the optimum voltage to the condenser be?
Help!!!
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Old 06-17-2016, 11:15 PM   #2
JSeery
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Default Re: Burning points??

Well, the coil is wired backwards for starters. What is the resistance of the coil and what is the resistance of the ballast resistor?
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Old 06-18-2016, 01:18 AM   #3
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Default Re: Burning points??

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Well, the coil is wired backwards for starters. What is the resistance of the coil and what is the resistance of the ballast resistor?
Not sure. I'll have to go get a multimeter.
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Old 06-18-2016, 02:23 AM   #4
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Default Re: Burning points??

Are both sides of the point burnt equally or have metal moved and buillt up on one side ?
If metal has moved to one side of the point the balance of the circuit is wrong (coil/capacitor value).
If both sides are equally burnt in a short time to high load is probably the cause.
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Old 06-18-2016, 10:55 AM   #5
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Default Re: Burning points??

The condenser may just be the bad item. If you have a 1.5 Ohm primary side type coil resistance and a 1.4 to 1.5 Ohm ballast, they should be good to go. Polarity mis-match usually just causes a weaker spark but who knows with the parts available now days. I'd check the components out and see what they add up to just to be safe and definitely replace the points & condenser.
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Old 06-18-2016, 07:09 PM   #6
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Default Re: Burning points??

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Quote:
Originally Posted by JSeery View Post
Well, the coil is wired backwards for starters. What is the resistance of the coil and what is the resistance of the ballast resistor?
The coil has 3.0 ohms across the terminals, and the ballast resistor shows 1.7 ohms.

Last edited by Bassman/NZ; 06-18-2016 at 09:03 PM.
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Old 06-18-2016, 07:15 PM   #7
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Default Re: Burning points??

Quote:
Originally Posted by flatheadmurre View Post
Are both sides of the point burnt equally or have metal moved and buillt up on one side ?
If metal has moved to one side of the point the balance of the circuit is wrong (coil/capacitor value).
If both sides are equally burnt in a short time to high load is probably the cause.
One side has a peak, the other, a corresponding valley.
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Old 06-18-2016, 07:17 PM   #8
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Default Re: Burning points??

So far, it looks like my coil is wired back to front, and the ballast is sort of ok, but the coil is showing too high of a resistance? Or is this OK for a 12v system with a 12v coil?

Last edited by Bassman/NZ; 06-18-2016 at 09:04 PM.
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Old 06-18-2016, 11:19 PM   #9
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Default Re: Burning points??

14v / 4.7 ohms = 3 amps, so that shouldn't be an issue. Do you have a starter bypass wired in? Is it wired correctly?
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Old 06-19-2016, 12:09 AM   #10
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Default Re: Burning points??

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14v / 4.7 ohms = 3 amps, so that shouldn't be an issue. Do you have a starter bypass wired in? Is it wired correctly?
No starter bypass.
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Old 06-19-2016, 02:08 AM   #11
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Default Re: Burning points??

You have metal migration on the points so capacitor value is not as it should be.
The coil resistance is on the lower end so that shouldn´t be an issue.
The balance of the points is set by coil/cap combination if cap value is low metal goes to one side if value is high the other side.
Try a new cap and points.
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Old 06-19-2016, 04:08 AM   #12
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Default Re: Burning points??

Quote:
Originally Posted by flatheadmurre View Post
You have metal migration on the points so capacitor value is not as it should be.
The coil resistance is on the lower end so that shouldn´t be an issue.
The balance of the points is set by coil/cap combination if cap value is low metal goes to one side if value is high the other side.
Try a new cap and points.
Thanks. I'll try a Bosch GH208-C condenser, that seems to work well for others. Also new points, and reverse the terminals on the coil.
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