Ballast resistorless coil damage



how much damage did I do to my 1960 TR3A when I have tried to use a coil w/o the required ballast resistor? The coil is too hot to touch after only a few seconds of trying to start the engine (which will not really start) and I have been trying this coil for three months. I had already converted to negative ground, alternator, and Mallory Dual Point ignition, which require the ballast resistor but my propensity For density over looked that small notation. I have had the TR for 34 years and this is really my first big goof.


All coils are 6V whether or not they have an internal ballast resistor. It is impossible to say whether the coil is damaged or not, but I suspect it isn’t. The wire can take well over what you can touch it at. Sparking would be a good sign, but a problem could show up at high speed if a couple turns are shorted. Just as a suggestion, I would recommend an old MSD-5 electronic ignition. I use these on my old flathead boat engines that I can run at a 300 rpm in gear idle for hours without fouling a plug. Above 1,000 rpm there is no advantage. That multiple spark sure gives a great idle with old engines.


Check the position of the stars, kill a chicken and walk three times sunwise around your car chanting: “Oh mighty Prince of Darkness protect your unworthy servant.”


Usually a system with no resistor will burn the points up. Some coil heating is normal but I’d question the too hot too touch part of it.

Why not add a resistor? These can be purchased dirt cheap at car parts houses and they’re dead simple to install. Install it in-line in the power lead to the coil AND make sure you tie from the small starter solenoid wire to the + side of the coil.
This will provide 12 volts in the START position (as it should be) and 6 volts only in the RUN position.


Thanks for the reply and info. I will look into an MSD-5 as it would sure make things easier. Thanks again!


Wow! the points were fried! I will look for an other coil, perhaps with an internal resistor and one that is known to be compatible with the Mallory distributor. I was wondering if any other part of the ignition electris may have suffered damage? Thanks very much for your reply. Very useful.


I see you may have used Lucas “Lords of Darkness - the lights go out when the sun goes down” electrics before? Thanks fro the post, I needed a good chuckle.


You should be able to use an old VW Beetle air-cooled engine ignition coil. Get one for a mid/late 60s/mid 70s model. The earlier VW Beetles were 6 volt systems.
These coils have an internal resistor and if you go this route should be able to plug and play with no problems.




I have a 1974 TR6. So I feel your pain


The Mallory duel-point offers NO advantage in a 4 cylinder engine. The STOCK system will work just fine…

A pointless electronic system offers zero maintenance and so would be an improvement.