Re: arrgh! ignition coil failure!

["Bert Hickman" <bert.hickman-at-xxxxxxxxxx> (by way of Terry Fritz <twftesla-at-xxxxxxxxxx>)]

Tesla list wrote:
> 
> Original poster: Hhchicken1-at-aol-dot-com
> 
> I don't think the dimmer's at fault, because I tried it with an ordinary
> switch, with the same result :(
> 
> Henry

Henry,

I'd bet that your dimmer's internal silicon controlled switch (called a
TRIAC) is short-circuited. Using a dimmer in this particular circuit is
very tough on it, since every time it turns on, it charges the capacitor
that's in series with your ignition coil(s) with a large spike of
current. Every time the AC mains polarity reverses, the voltage across
the TRIAC is actually about twice the line voltage because of the charge
that's retained by the capacitor, and all the following current spikes
can actually be twice as large as the very first one. In effect you are
operating your 220 volt dimmer off a 440 volt circuit! It's not
surprising that it may have failed, since it is likely the "weakest
link" in the circuit. 

If your TRIAC is shorted, then the ONLY time you'll get a spark is when
you first turn on power to the circuit. If you use a regular on-off
switch, you'll see similar behavior when you turn the switch "on". The
fact that you get a single spark says your ignition coil(s) are good,
and the capacitor is good. If the capacitor was shorted, you would blow
your mains circuit breaker or fuse, and if it were open circuited you
wouldn't get any spark at all. 

I bet if you connected a lamp in series with your dimmer, you'd find
that it lights at full brilliance. 

Safe coilin' to you!

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com