8N Ballast Resistor Specs

That resistor won't work, as you found out. The
OEM Ballast is available at NAPA or other ~$7.00 Stand alone(W/O Block) and will work fine by itself as long as that coil is really 3.3 ohms.

Just for reference: W/O Ballast (E X E)/R (14.5 x 14.5)/3.3 = 63 Watts. We know the Front Mount coil fails for sure @ 50 watts. With the OEM Ballast "coil" wattage drops (9.6 X 9.6)/3.3
= 28 Watts. Top of coil voltage (12.5 volts) 8.0 - 9.0 volts

BTW: Resistors are marked (resistance) on "one" of the Electrical connectors. One number on each side of the HOLE. (metal punch)

Regards,

This is old and dog-eared, done by someone on this Board (Ill) in 1997. It checks out as accurate. The response is "not" thermally delayed, as some have suggested.

The VD across the Ballast is ~4.5V @ 3 amps or (IXI)XR (9)x 1.5 = 13.5 watts Worst Case.
The Max wattage of most Ballast's is near 20 watts. The Wattage of Resistive devices will depend on Surface area and its thermal treatment. The Metal shield helps the OEM Ballast dissipate >10 watts of heat, but its "intended" to be limited.

I will try and find the Ballast's response Curve and POST. It will answer your technical questions, but you do need to think like a coil!

Phil,

You know of course, you can ALWAYS OVERSPEC WATTS of resistors. Iff'n you undespec resistor watts, guess watt??? kaboolie..... blown resistor. Good electronic engineering practice is overspec watts by factor of 3-time. (minimum)

Don't forget the real reason for the "infamous ballast resistor" was weaksister 6-volt batterys. They didn't make die-hards back in 1939.

And by making the "infamous ballast resistor" out of temperature sensitive resistive element, Ford automatically OVER-VOLTAGED the ignition coil when COLD and the 6-volt battery was weakest. The ballast resistor would automatically heat-up and increase its resistance to a nominal 0.7ohms in about 2-minutes running time. (ballast resistance varies from about 0.3ohm to 1.4ohm, depending upon its internal temperature)

You do know that the squarecan ignition coil is really a 3-volt and 3-amp ignition coil, don't you? And that the infamous ballast resistor is NECESSARY to drop the 6-volt battery down to about 3-volts.

I've seen all sorts of schemes to by-pass the MANDATORY & NECESSARY infamous ballast resistor for hotter-sparkies and quicker starts. They all have one great "weakness", they will MELT the squarecan insulative tars in about 1-hr and short-out internal windings and you endup with weak sparkies..... ....Dell, yer self-appointed sparkie-meister

I picked up an ICR-13, subbed to RU4 BW (marked 1.8) today and my Fluke measures 2.2... that is strange, unless its PTC! These auto ignition resistors are not what they claim (BOOK), most likey manufactured in Mexico.

Regards,

For my old front mount, if my "warmed up" voltage is approximately 3 volts with the points closed, I figure it's good to go...

Electricity, obeying the rules it always does, can usually be managed via voltage control. Also that's why knowing the charging voltage is more beneficial than knowing the amp flow...

Post back how the old and new compare if you get it figured out...

duey

If you know the full series resistance ( or inductance as the case may be ) in a circuit.. and or the voltage, and or the current flow.. you can get the other variables out of E=IR

System votlage is easy to check.. series cuurrent is easy to check.. and total primary ressitance can be extrapolated from there..

Vdrop across the resistor can be measured as well as Vdrop across the coil... Thus you can calculate resistance respective resistances of the parts in question.

Soundguy