Hello,
I am in the process of returning my spider to points. My question is about the coi.l I understand that the original coils were 1.5 ohm and required the ballast resister, however the coils I have found for sale today are 3 ohm and say not to use with a ballast. So do I bypass the ballast and run the ground wire from the distributor (points and condenser) to the negative of the coil? Or do I still wire it thru the ballast?
Thanks.
Ballast resistor yes or no?
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70spider
- Posts: 676
- Joined: Fri Mar 14, 2014 3:05 pm
- Your car is a: 1970 Fiat spider
- Location: N.E. New Mexico
Ballast resistor yes or no?
1970 Fiat Spider 124 Sport aka "Pesto"
2002 Mazda Protege5
2013 Buddy 170i
2002 Mazda Protege5
2013 Buddy 170i
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18Fiatsandcounting
- Posts: 3798
- Joined: Fri Mar 15, 2019 11:23 pm
- Your car is a: 1969 and 1971 124 spiders
- Location: San Francisco Bay Area
Re: Ballast resistor yes or no?
Early spiders work well with a total primary circuit resistance of about 2.5 ohms. So, if you have a 3 ohm coil, you don't need a ballast resistor. You could still use the resistor and it would probably work, but the spark wouldn't be as hot.
You're right, the original coil was about 1.5 ohms plus a 1 ohm ballast resistor for a total resistance of 2.5 ohms.
If you use a much newer coil with less than 1 ohm resistance, you definitely need a ballast resistor. The smaller the overall resistance, the higher the current through the circuit, and with low resistance coils, you run more amps through the points than they were designed for.
To bypass the resistor, you just run the wire from the distributor directly to the negative terminal on the coil. The brown tachometer lead would also connect there as well.
-Bryan
You're right, the original coil was about 1.5 ohms plus a 1 ohm ballast resistor for a total resistance of 2.5 ohms.
If you use a much newer coil with less than 1 ohm resistance, you definitely need a ballast resistor. The smaller the overall resistance, the higher the current through the circuit, and with low resistance coils, you run more amps through the points than they were designed for.
To bypass the resistor, you just run the wire from the distributor directly to the negative terminal on the coil. The brown tachometer lead would also connect there as well.
-Bryan