You really do need to diagnose the problem first
If your car has a ballast resistor in the ignition circuit, the current to the coil goes through the resistor after starting (ie when the engine is running). It is bypassed only when the starter motor is operating (ie during the few seconds it takes to start the car).
This means that the voltage on the coil (when running) will be less than the nominal 12V from the battery (by design) and the coil is specifically rated for that lower voltage - usually (most Lucas designs) have 6v drop over the resistor and a coil that is nominally rated for a 6v system.
During starting the resistor is bypassed (bridged out) and the full battery voltage is applied to the coil to aid starting (ie the coil is overdriven for a short time). This is fine as long as the car starts qucikly - the coil can stand the over voltage for a short time.
Assuming that the resistor is working as designed, and the coil is correctly specified, a couple of things come to mind - 9.5v on the coil looks fine for a ballasted system (actually a bit high, I'd expect 7-8v, but that depends on the actual resistor).
If you bypass the resistor when the fans are on, you will burn out the coil relatively quickly.
Does your car have the chrysler electronic ignition (my early 412 did, and the late 411s are very similar) - if so you should check that out, they are rather prone to failure in unusual ways (and are getting very old).
Bottom line - the coil voltage is unlikely to be the culprit. Your suggest fix will cause the car to fail to proceed.
Something else is happening here.
Hope this is helpful
Regards
Julian
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