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TR2/3/3A TR3 Coil Problem ??

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mapleaf

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While on a run in the 3a last night it suddenly died but after a few minutes it restarted but wouldn't keep running. This morning it started and ran for about 5 minutes, stopped and wouldn't restart. I've eliminated the fuel pump and points (new) as possible causes and I'm now thinking that the coil is the culprit. This is what I noticed after the engine running for 5 minutes this morning. The coil was extremely hot to the touch and there was juice at the sw connection but none at the cb connection to the distributor. Sound like the coil???
If it is, are coils generic and can I swap it out with any other 12V coil or find the right one at NAPA?

Thanks
 
Being very hot might indicate a problem; but no voltage at the CB connector might just mean the points were closed.

I would be surprised if you can find a coil at NAPA that does not require an external ballast resistor. However, they should have a ballast resistor also available. The other issue might be the high voltage connection; modern coils take a push-in clip that contacts the sides of the hole; unlike the original TR coil where the wire contacted the bottom of the hole. But they should also be able to sell you the parts to convert your coil wire to a modern push-in terminal.

If you should decide to replace the high tension wire from the coil to the distributor, I would suggest finding a solid-core wire. My experience has been that the 'carbon' core wires that most modern cars use will quickly fail at the point where the screw pierces the insulation.

Of course there are push-in type caps available as well ... :devilgrin:
 
It may be worth swapping the condenser as they are liable to fail and give similar symptoms. The coil can get very hot in operation, but it sounds as though yours is rather too hot too soon after starting up.
My most recent misfire was caused by a corroded HT terminal on the coil. Many modern replacement rotor arms don't last well and it would be worth swapping it for a known old one to see if that helps.
 
Thanks guys.
Randall, if the points are closed with the ignition left on would that cause the coil to heat up over time?
Well, I decided to look at the points again as the possible problem partly because I installed a new set last week and it ran alright up until then.
Just a thought, but when I compared the action of the points closing, the new set seemed sluggish compared to my other sets of spare points. Spring pressure doesn't seem as strong. Anyway, I replaced the points and condenser, cleaned up all the terminals and let the car run at fast idle for about 1/2 hour. Seems to be okay now but I'm still a concerned about the coil so I ordered a new one to have on hand. Next time I take it out on the road I'll make sure I have all my tools and spare parts with me. I'm sure the motor league must have a limit on tows.
Thanks again
Barry
 
mapleaf said:
Randall, if the points are closed with the ignition left on would that cause the coil to heat up over time?
Click to expand...
Yes, it will get quite hot under those conditions. It will be drawing something like 40 watts, which all gets turned into heat.
That's actually why the coil itself is in that metal can filled with oil; the oil helps carry heat from the windings out to the surface of the can.

PS, think of how hot a 40 watt light bulb gets.
 
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