Discussion
Basic question. A 1984 280i has an inline ballast resistor. Well, mine has, mounted on the front by the radiator. Therefore I assume the coil is 9 volt coil? I've recently acquired a new Sparkrite coil with an external ballast resistor mounted on the side. Compatable? Options, (a) Short out the present resistor and attach the + feed to the new coil resistor, or (b) Retain the original resistor and connect the + feed direct to the coil. Thoughts please? Thankyou. J C.
Good question Mike. Obviously current can only be measured whilst cranking. Circuit diagrams are not that informative as to how the ballast resistor is wired in? Logically one would assume in series with the supply to the coil? Logic and TVR!! So will try your suggestion and use the resistor that came with the coil and short out the original one. Thanks J C.
Some ballast resistors are bypassed when cranking, either with an extra terminal on the starter solenoid, or perhaps a relay.
When you are cranking the battery voltage drops markedly to around 9V. So with the ballast bypassed, the coil now gets its normal supply voltage, and you get a full fat spark just when you really need it.
When you are cranking the battery voltage drops markedly to around 9V. So with the ballast bypassed, the coil now gets its normal supply voltage, and you get a full fat spark just when you really need it.
Thanks for the replies. The coil arrived with various connection options detailed. Basically, if you already have a ballast resistor fitted connect the + straight to the coil; if not use the resistor that comes the coil in series with the + feed. I'm sure mine has only one + wire to the coil so therefore I'm assuming the ballast resistor mounted on the front of the engine bay is in series with the + feed. Cheers J C.
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