The Triumph 2000 / 2500 / 2·5 Register Forum

If the car burst into life when the AA man bridged out the ballast resistor (having already said the spark was a bit weak) I wonder if the coil is a 12V version anyway? They should have it printed/stamped on them somewhere, but a definitive test is to measure the coil resistance. A 12V coil is usually around 3 ohms, a 6V coil 1.5 ohms. Ish. Or you could measure the static coil current (with the points closed). A 12V coil about 4 amps, a 6V coil about the same! A 6V coil on 12V would be nearer 8A.

Good luck!

Cheers,
Mike.

Hi Mike

I can't get to that side of the engine bay at the moment but I'll have a look when I get the car out when the latest parcel from Chris arrives...

Hello Trevan,

"If the car burst into life when the AA man bridged out the ballast resistor"

A sure fire indication of a faulty ballast resistor circuit is that the car will start when cranked but immediately die when the ignition key is returned to the run position (Always assuming the by pass from the starter is working?). It can be that the termination on the wire to the resistor is poor rather than a failure of the resistor itself? (I had that problem with my Scimitar when I first bought it, a new terminal and its been fine ever since.)

Alec

Hi Alec

She does do exactly that! Sometimes she starts, sometimes not but she will also seem to start but dies away as the key is released from my hand. (I hadn't really thought of it as a different form of not starting until now). I replaced all the terminals when I replaced the resister but she still did that. I am in a bit of a weakened state following my surgeries but I had the AA man check (rather begrudgingly) that the terminals were secure.

I decided to go for a 12v Lucas Sports Coil in the end. Chris does them for £15 so I figured that, if it cures the problem, I'll know it is the ballast resister circuit or the coil itself and that I can easily go back to standard whilst being able to get out and about in the meantime. The way I'm feeling at the moment, that's definitely worth £15! I'll carefully check the electric fuel pump wiring at the same time and try the ignition switch if the problem persists.

Wish me luck!

Trevan

Hello Trevan,

good Luck .

If you suspect a problem with your ignition switch, check the voltmeter when you crank the engine (Because of the nature of the voltmeter you may need to wait a minute first so it registers.). If there is a switch problem or the supply to it then the voltmeter will register a low voltage, if not and it's still not starting then it's not the ignition switch. Admittedly not an ideal test as the instrument is slow to react, but I would expect to see something?

Alec

Totally agree with Alec's comments about the ballast resistor. In normal running it is in series with the coil to reduce the actual coil voltage to ~6-8V. However, during starting, a direct 12V feed comes to the coil from the starter motor, effectively bridging out the ballast resistor. Hence a problem with the resistor lets the engine fire when cranking (via feed from starter motor) but when you let go the key, the coil gets nothing via the resistor.

With your new 12V coil you should feed the '+' end from an ignition supply - 'top' end of the ballast resistor, or if a PI, the inertia cutout.

Do also remember that the reason for a 6V coil and resistor is that under cold cranking conditions, the battery voltage will drop a lot so the coil doesn't see 12V but maybe only 8-10V. These cars were originally designed for sale anywhere in the world, including very cold places - far colder than the UK - so this may not be an issue here!

Sorry if I'm teaching granny etc!

And, of course, good luck!

Cheers,
Mike.

Mike - educating Granny is closer to the mark!

Alec - hoping not to have take any of the interior apart but I'll have a play with the multimeter if I do...

Thanks everyone for their input - this is a very reassuring place for the mechanically challenged!

hello Trevan,

it seems as if I misled you, I was talking about using the car's installed voltmeter, no dismantling or multimeter required.

Alec

Hi Alec

More misread than misled... Makes much more sense now!

Trevan

Hi Guys

The latest box from CW arrived this morning and I got the 12v coil and the latest rotor arm fitted and I'm delighted to say that I've just got back from an hour of smoking around without the car missing a beat. It took awhile for me to relax but once I did I had great fun!

Thanks everyone for their comments, advice and support!

Trevan