924Board.org

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I'm resurrecting my partially restored 931, 1979. Its a car that was running 8 years ago when I parked it, but I didn't drive it much, just a few miles.

After deleting an old alarm system I keep finding old "solutions" to presumably old problems.
Right now its the coil. Power to it is cut when I crank so I assume its connected to the wrong power leads.
So last night during some investigating I hear something bubbling, immediately checks for fuel leaks, no, it's the coil that's boiling!! It gets feed power straight from the battery when the key is on! There is supposed to be one, maybe two, ballast resistors in the system according to the Haynes schematics. 1 Ohm from the starter cranking and 1.5 Ohm from the ignition (or maybe between the ignition box and the coil).

Do you guys know where the ballast resistors are supposed to be located?
Haven't boiled a coil before, is it toast now?
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/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe

[924RACR]

I seem to recall that at least on the NA '79, the ballast resistors are actually built in to the wires leading to the coil.

Seems like the coil is toast - and I have trouble believing it should burn or boil out just from getting 12V. Maybe a short to ground through the ignition box or something like that?
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[safe]

You're right, the wires themself have a resistance. Fixed some wiring, replaced the coil and it started, sort of... it runs very badly on 2 or 3 cylinders.

12 volt directly to the coil is about double the normal operating voltage, so it will fry them.
_________________
/Magnus, Stockholm Sweden
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Porsche 924 -79 NA, EFI and Turbo.
Porsche 931 -79
Porsche 911 -77, 3.2 Targa
Porsche 911 -69, 3.6, Coupe