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Re: Is there a ballast resistor for a 1971 96 ??? Posted by eric in vermont [Email] (#2058) [Profile/Gallery] (more from eric in vermont) on Sat, 28 Feb 2009 09:10:22 In Reply to: Is there a ballast resistor for a 1971 96 ???, Slyde, Fri, 27 Feb 2009 17:35:43 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I've never seen a ballast resistor on any of my VSAAB cars, but I understand that some Vintage Saabs may have them.
The bottom line is this: there must be some resistance in the coil circuit and it may show up internal to the coil or external to the coil.
If you measure across the primary of the coil (with the wires disconnected) you should get:
A. 4 to 4.5 ohms. This means the ballast is inside the coil, no outside resistance is needed. Life is good.
B. 1.5 to 2.5 ohms. This means you NEED an external ballast resistor of 1.3 to 2.0 ohms. Add that and life is good.
Now, the condenser comes into play here is well. If you're burning points, then it can also be your condenser that's bad or disconnected. The Saab condenser is really a capacitor and should have a value of about 0.22 microfarads. These dry out over time and if the cap is too small, your points tend to burn up. This is because the coil has lots of inductance. When the points open, the coil voltage wants to go to infinity because that's what inductors want to do in life (actually, then want to keep their current flowing and when the points open, the voltage increases immediately as the inductor "tries" to keep its current flowing). The condenser limits the voltage surge because it doesn't want to change it's voltage quickly. The lower the capacitance, the bigger the surge of voltage and the more the points burn. However, too big a value of capacitance will not allow the voltage to build up enough, limiting the voltage to the plugs and causing poor firing. Most people don't have a capacitance meter hanging around, and it's not possible to check these with an ohm meter, so changing them out is the best way to fix a suspected problem.
Electrical engineering 101.
So check your coil resistance and your condenser. Correct components should fix your points problem.
eric in vermont
posted by 68.142....
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