Re: Ignition coil exploded

[david crooks <david.crooks@xxxxxxxxxxxx>]

>The other coil that died quickly also seemed
>to be when I was working on the car and had
>left the key on quite a bit.  Seems like that
>is overheating the coil.
>
>Any other possible causes?  The car starts and
>runs fine other than blowing up the coils!

Hi Colin,
Ballast resistor or not, Ignition systems are
NOT designed to be powered up for long periods
without the engine running.  Their DC resistance
is fairly low, which means lots of heat.

When the engine is running, the voltage to the
coil is really an AC voltage, created by the points
opening and closing.  The AC impedance of the coil
is much higher than the DC resistance, so less current
and less heat while the engine is running.

That's one of the reasons for the "Accessory" position
on the ignition switch...  To let you run the radio
without blowing up the coil!

Cheers,

Dave