Could a Coil...

[Maxwell]

A] Just die without warning, parked in a dry Garage; and,
B] If it did die, would it stop the IGN light in the dashboard from illuminating?

Thanks in anticipation... Maxwell

[whitenviro]

Yes. This wasn't a TR7, but I had the coil die on my Volkswagen van while it was just sitting there idling. 70 miles from everywhere. That little incident is what made me build up a stock of repair parts that went with me everywhere we took that van.

But since it wasn't a TR, I don't know if it would affect the dash light.

[John_C]

If the dash light is out that would break the circuit and mean you would have no ignition.









Okay, I made that one up.

[Spike]

Not sure about the ignition light - but when I was looking at my current 7 the coil failed. Been ticking over for ten minutes, just sat down to take for a test drive and it just died!

Still bought it after they'd replaced the coil

[dmtrmp6]

This may be a little long but . . . . The ignition light on dash cluster is part of the alternator excitation circuit. Basically when the ignition switch is turned on, 12 volts is supplied to the alternator via the ignition (ign) light which will allow the alternator to provide an output once starts spinning. Whilst this supply is present there is a current flow through the ignition bulb which is why it glows when key is initially turned on. (This excitation allows a magnetic flux to be developed and therefore the alternator to develop an output to charge the battery, power accessories etc).
Once the Alternator begins to develop an output to the battery, it also feeds 12 volts back to the opposite side of the ignition light - so now 12 volts on both sides of the bulb therefore no current flow or voltage difference and the ign light is extinguished. If the ign light remains on when started then it normally indicates a battery supply or alternator problem.
This "ignition light" circuit is somewhat mislabelled as it is not directly connected within the ignition coil circuit. For info, if the ignition light does not light when the ign switch is turned on it is usually due to a loss of battery supply to the bulb (and onto alternator), a blown ign light bulb, or an open circuit in the alternator or ign switch wiring.
If the bulb remains on at a dimmed level once started this is often a sign of worn alternator brushes or blown diode within the alternator.
Depending on what year your TR7 is they use a ballast resistor in circuit with the coil which is actually a long piece of resistive wire ("pink") embedded in the wiring harness. It is unusual for a coil to just blow, unless there is a problem in the coil winding, or possibly the alternator is overcharging, or the car has been allowed to sit with the ignition active - but car not running - this constant current flow for extended period can burn out a coil. If you have an ignition system with electronics (factory Delco or Lucas Opus) it may be possible if the altertnator is overcharging to damage the electronics, or they have been known to just fail, particularly the Lucas Opus.
Ign supply to the coil is via the ignition relay (behind glovebox) or sometimes from extra terminal on starter motor. either of these supplies could fail.
Hope this is helpful, Rgds, DM

[Hasbeen]

I had a very faint hesitancy in my 7, when accelerating very gently, when cold, for years. It was so slight many could not detect it.

I fitted new terminals on the coil & other ignition wires, & thought I'd fixed it. It was back a year or so later. I progressively fitted new connector fittings, new ignition & spark plug wires, coil, ballast wire, & a few other things. Each attempt led to a few months & up to a year or more of no problem, but it always returned.

Finally the hesitancy became a dead cut out for a second or more, every now & then, perhaps once every 100 kilometres or so, particularly when cold, never when hot, accompanied by the rev counter dropping to zero.

In desperation I threw out the Lumenition system, & fitted a new different system. EUREKA, no repeat of the problem in about 4 years.

Hope this helps.

Hasbeen

[Maxwell]

Thanks for the help and advice guys - Big Thumbs Up!

Maxwell