Jake writes:
I am wondering if a 73 spit needs a ballist resistor. The car starts and
runs great but there is no ballist resisitor. Do I really need one.
The>comm numbers are FM1531U
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Chances are, unless the previous owner changed the coil to a non-ballasted
coil you will need a ballast resister. The purpose of the resistor is to
drop the voltage to the coil while the engine is running. A ballasted coil
runs at a lower voltage. This is to help during starting as the starter
draws considerable current and lowers the available voltage to the coil
during cranking (usually when you need a hot spark the most i.e. cold
morning). When you turn the key to start, it also switches out, or
by-passes the ballast resistor so that you get roughly 8-10 volts (because
of the above mentioned condition) at cranking. When you release the key
after the engine fires, the resistor is re-connected to drop the voltage to
roughly the same as when the car was cranking. This is so that you don't
burn out the coil by running it at a voltage/current that it was not
designed for. By running a ballasted coil without a ballast resistor you
run the risk of burning it out. The only way to tell what coil you have
(unless it is marked) is to measure the primary resistance of the coil.
The resistance will be lower for the ballasted coil, unfortunately I don't
have that information. Possibly someone on this list can help you there.
Barry Schwartz
Bschwartz@encad.com (work)
Bschwart@pacbell.net (home)
(San Diego)
70' Spitfire (minor surgery started) , 72'-V6 Spitfire (daily driver)
70'GT6+
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