[TR] and a bad coil?

[Randall]

> Query:  A ballast wire or ballast resistor is ony about 5-10 Ohms,
> right?  Just wonder what I should look for if I put a meter on it.

Usually much smaller than that, around 1.5 ohms.  Best check IMO is to turn
the engine until the points are closed (or install a jumper to simulate
points closed) and check how much voltage you have at the coil.  With no
ballast, should be darn near battery voltage.  If it's less, you may have a
ballast or possibly something else limiting current, like a bad connection
or a dodgy ignition switch.

> The coil is a Lucas Sport, was on there when I
> bought the car about 7 years ago.  

Contrary to what some people believe, Lucas Sport coils come in both
flavors.  Check the part number/markings before assuming that it does/not
need a ballast; or measure the primary resistance.

> What are the usual symptoms when a coil fails?

Beats me.  I don't think I've ever had a failure that wasn't obvious, like
broken plastic or leaking oil or open circuit.  I pulled the motor from the
former daily driver TR3A the other day, and it's still wearing the coil from
K-mart back in 1986 or so.

> And is there any real advantage of one coil over another?  I can't
> see why there should be.  That might matter if I put on a new coil.

Do you mean ballast vs no ballast?  IMO only advantage is in cold weather,
when the ballast bypass circuit gives a bit more spark energy for easier
starting.  Likewise the "high output" coils are only helpful in situations
where you might get a misfire otherwise, like starting from cold; tired or
fouled plugs; mixture not all it should be, etc.

That said, I ran a MSD 6 ignition for many years on the daily driver (the
K-mart coil was because the MSD toasted the old Accel coil), which will
produce lightning bolts from pretty much any coil.  Did start easier, but no
noticeable "seat of the pants" difference once the engine was running.  I
kept it mostly because it made the points last forever.

When the MSD finally died, I switched to a Crane XR3000 to compensate for
the worn distributor.   Never did run quite as crisply with the Crane as it
did on either points or MSD, don't know why.

Haven't quite decided what to do with the project TR3; but for now it's
running just fine on 30 year old points.

-- Randall