TR2/3/3A TR Mystery Thingy

[ckeithjordan]

The PO installed this white thingy next to the condenser on the engine of my newly-acquired 1957 TR3. Any ideas what it might be?

 

[ckeithjordan]

It would help to attach a photo of said thingy. Sorry about that.

 

[M_Pied_Lourd]

Did the car have a radio in it? Wonder if it's some sort of aftermarket noise suppressor.

Cheers
Tush

 

[ckeithjordan]

No radio with the car.

 

[Roger]

Ballast resistor? But then I'd expect to see another wire to that coil terminal, from the starter circuit, to provide 12v for starting.

 

[TRopic6]

Yep, that's a ballast resistor, and looks like it powers the coil through the white ignition wire. The coil should be 1.5 ohms or so to work in series with it.

Jeff

 

[ckeithjordan]

Thanks, Jeff. I meant coil when I typed condensor (though technically the condensor is near there in the distributor housing). Why would there be a "need" for a resistor?

 

[bobhustead]

Without resistance, either built into the coil or external as here the system is a dead short.

Bob

 

[Geo Hahn]

...Why would there be a "need" for a resistor?

To accommodate the use of the 'wrong' coil (e.g. I think a coil for a late TR6 would require that 'thingy' to be used in a TR3).

 

[CJD]

Many high performance coils have lower resistance, and require an additional ballast resistor. I think the idea of a lower resistance (impedance), is the coil is able to charge faster, so the spark is stronger at high RPM, when the sparks are close together.

 

[Geo Hahn]

Though the most common 'wrong' coil will be one made for an ignition with a resistor wire (like the TR6) that is bypassed during starting for more coil output while cranking.

 

[TexasKnucklehead]

The first post made me think that you may have been too close to the white thingy when you took the picture, or the engine was also white and very very clean -sort of like that white cow in a snow storm sort of thingy. But the mystery of the white thingy (which is certainly a ballast resister) is that with only one wire between it and the coil, there is no 'hot' feature where the full +12v is powering the coil while starting. If you are not having any trouble starting the engine when cold, I'd let it be. There's nothing 'wrong' about running a ballasted ignition, but TR3s predated the crazy anti-pollution methods attempted and generally use a coil rated at the full +12v, instead of the lower rated coil. If you want to remove the resister, be sure to also replace the coil with a 'right' one.

If you ever have an ignition failure and want to check to see if the resister has failed, you can simply short across it and see if ignition is restored. If you try to run any significant length of time with the resister shorted, and a 'ballasted' coil installed, the coil will fail. In other words, you can short it out for a test, but not for very long. If you are the curious type, you can start the car and measure the voltage at the input (white wire) and the output (wire to coil) and see how much the ballast is dropping the coil voltage. My guess is you'll see from 12v to 14v depending on engine RPM/generator/alternator output on the white wire, and about 9v on the coil side.

 

[sp53]

For some reason, I just remember my auto shop teacher in 1969 saying: “a car starts on 12v but runs on 6v” anybody remember that? Or maybe it was a car starts on 6v then runs on 12v--But, yah that is a ballast resister, so you do not cook your points and condenser by getting too much voltage from the coil. I would get rid of it and go stock. I also remember back then you could get a special wire from the ignition that would reduce the voltage too.
steve

 

[ckeithjordan]

Thanks to all who responded. I think I'll take it back to stock. TRF has the parts on sale at a good price, so it's a good time to do it.