9N resistor

That new coil that measures 2.5 ohms is close to what a standard 12 volt coil would be as they are often in the 2.5 to 3.5 ohms range. I would try it first unballasted and see how warm it gets but if it gets so hot you cant hold your hand on it, thats too much current and it needs ballast. If you overballast then the coils not gonna draw as much current as it was designed for and the spark will be weaker taking away the benefits that elec ignition has to offer. When one uses an elec. switch I recommend it be coupled with a high energy performance coil to get the most bang for the buck that elec igniiton has to offer.

I believe Id try that new coil unballasted first n see if it overheats and if so THEN add some ballast between .5 and 1 ohm.

John T

I don't know if you follow the Ford "N" board, but problems come up quite often with the so-called "square" aftermarket (READ "china") 12-Volt coils for the front-mount distributors.

It seems they are not as "robust" as true 12-Volt "round can" coils, and Dell always recommends the 1/2 Ohm current limiting resistor with the square coils, and a lot of folks, myself included, have had better luck with those coils when the 1/2 Ohm resistor is used.

I have not yet used an electronic conversion on one of these units, so I don't know if the resistor is needed, since the added forward voltage drop across a semiconductor junction occurs with the electronic units, but I figure if he is having trouble, the resistor is worth a try!

If experience or specs show that coil needs ballasted that 1/2 ohm shown ought to do the trick. Assuming, however, if the coil can be used at a full 12 volts AND CAN TAKE IT WITHOUT OVERHEATING then the spark energy would be less if it were ballasted.

It cant hurt to be oversafe I reckon and use the ballast, we cant really say unless we had detailed coil specs n data which we dont have grrrrr rr

Yall take care, thanks again Bob

John T

Dell came up with his .5 Ohm resistor based on what used to be supplied along with the aftermarket coils some years back, and using 2- 1 Ohm 10 Watt resistors in parallel provides a readily available and economical source for a resistor of that value.

The typical Dodge or other standard off-the-shelf ballast resistors are typically 1.4 Ohms, 1.5 Ohms, 1.6 Ohms, or 1.8 Ohms, WAY more resistance than is required for this application. Too much resistance leads to a weak spark, causing hard starting, and perhaps misfire when running.

However, the off-the-shelf resistors work just fine with 6-Volt or "use WITH external resistor" 12-Volt "round-can coils".

So we are talking about 2 different "animals" here... the "oddball" aftermarket square can 12-Volt coil for Fords with the "front-mount" distributor, vs. 'most other applications with the more standard and robust "round-can" coils.

I completely agree with you about using the "Dodge", or similar, resistors in MOST 12-Volt conversions, HOWEVER, Dell is "on the money" with the 1/2 Ohm resistor for this ONE SPECIFIC APPLICATION... the "12-Volt" square-can aftermarket front-mount Ford coil.

This is used on "12-Volt" coils on front-mount distributor 12-Volt conversions still using points, and it would be worth a try on a unit with an electronic module, as is would serve the same purpose.

It is 2 - 1 Ohm, 10 Watt resistors in parallel, making a 1/2 Ohm, 20 Watt resistor.

(Credit Timw(Pa) from PA for the photo.)

this gets you a 2-pack of 1ohm, 10watt resistors which you parallel as bob showed to get a .5 ohm, 20 watt resistor.

Soundguy