testing for the existence of ballast resistor in my car
 

what's the simplest way to test for whether or not i've got a ballast resistor in the circuitry that runs from my ignition switch to my coil on my '41 ford? as i think i've finally found the reason that my E-Fire distributor is not working. i.e. it will apparently (buried very deep in the small print in the installation manual) not work at all with a ballast resistor, and i suspect my car has one.

and if i do have one, what's the best way to bypass it? hopefully one that doesn't involve laying upside down underneath the dash with both arms raised above my head for any more than a second or two. :)

Re: testing for the existence of ballast resistor in my car
 

On the 41 pickup its on the firewall under the rivers side dash. To bypass it simply place both wires on one stud. Tim

Re: testing for the existence of ballast resistor in my car
 

thanks. i saw it up there on my car too. but reaching it, let alone removing and attaching wires looks to be quite difficult as laying on the floor my arms are simply not long enough to even reach anything up there. could they have made it any more inaccessible? i'm thinking maybe it would be simpler to run a new wire from the ignition switch to the coil.

BTW, am i correct in thinking it's just a bit of ceramic inline with the ignition wire that when cold creates little resistance but heats up when 6v starts coursing through it and when it heats it becomes slightly more resistant and reduces the voltage to the coil thus putting less stress on it and the points. ...or something along those lines?

Re: testing for the existence of ballast resistor in my car
 

All you have to do is move either the red-black wire or the red wire connected to the resistor so both wires are attached to the same resistor post.

https://www.fordbarn.com/forum/attac...8&d=1772461274

https://www.fordbarn.com/forum/attac...9&d=1635130955

If you wish to check the resistance, disconnect the red wire from the coil. Now check the resistance from the ignition switch to the red wire end you disconnected, noting that the resistance will rise as it heats up.

Re: testing for the existence of ballast resistor in my car
 

ah!!! i think i see...

assuming the resistor is cold, when i turn on the ignition switch the resistance will be at it's lowest and steadily increase as time passes. can we assume that to make a second test, one would have to wait for it to cool down? and can i assume that it cools very quickly indeed, such that once the voltage is removed, restarting these cars BITD was not problematical?

Re: testing for the existence of ballast resistor in my car
 

Yes, that is how the resistor works.

Re: testing for the existence of ballast resistor in my car
 

As you mentioned, DON’T use the resistor with a Petronix module.

When starting with points, the resistance is very low and helps when starting. Once started, the resistor heats up increasing resistance and protecting the points from burning.

Re: testing for the existence of ballast resistor in my car
 

thanks guys, ...big help! should give me a couple of things to do. hopefully i can get my E-Fire distributor to work once i remove any ballast resistor that's in the circuit or failing that i can remove my traditional coil that's giving me fits, bypass the ballast
resistor and install my "modern" coil conversion kit and be done with the necessity to protect the points.

Re: testing for the existence of ballast resistor in my car
 

Points can be field adjusted and won’t leave you stranded

Re: testing for the existence of ballast resistor in my car
 

I have tested the output voltage of four original resistors and one aftermarket resistor. As they warmed, each dropped the voltage by only 0.2-0.4 volts. A few tenths of a volt seems to me to be negligible.

I think the theory of the higher voltage when cold to help starting is a myth. That technology did come into common use during the fifties, but then the resistor was actually by-passed during cranking. Not on our cars.

Re: testing for the existence of ballast resistor in my car
 

This is intentional. Part of the reason is that it can get very hot and you don't want to accidentally touch it.

Re: testing for the existence of ballast resistor in my car
 

understood...and they've succeeded beyond their wildest dreams AFAIC. :)

Re: testing for the existence of ballast resistor in my car
 

No myth and if not necessary to protect points why did the manufacturers spend the money for them?

Regarding, "not on our cars", the resistance is nil when cold. Now if you have trouble starting up your old Ford, the warming resistor can impede a quick start.

Re: testing for the existence of ballast resistor in my car
 

The ballast is to control the current draw of the old original type coil. Electricity works a lot faster than I do. A resistor will go to max heat the moment the circuit is closed. The old coils were a special design that couldn't reliably take a full current draw of a good 6-volt battery.

The breaker points are protected by the condenser. They are also constantly opening and closing the circuit to get the half wave pulsating DC current that allows the coil to function. This tends to drop the voltage and current a little bit as well but it's a negligible amount.

In the early 12-volt era, Chevy vehicles had a full 12-volt connection to the starter relay that boosted the ignition voltage for starting only. As soon as the engine was running, the circuit would revert back to the ballasted ignition switch wire.

Re: testing for the existence of ballast resistor in my car
 

Huey, if you were old and decrepit like many of us here, you’d know that your cel phone camera can be your eyes under your dashboard, saving you the upside down position on your back. Take a pic of the resistor’s connections to determine if the circuit goes through or bypasses the resistor.
To discover if it is connected without any of that, test the voltage at the ignition switch and compare that to the voltage at the coil while ignition is on. If your engine had stopped with points closed, with a resistor, you’ll get a reading of about 2 volts lower than at the ignition switch. Points open reading will be equal to the reading at the switch.

Re: testing for the existence of ballast resistor in my car
 

Don't forget Supereal's "Quick Start" circuit/modification...
https://www.fordbarn.com/forum/attac...9&d=1742506016

Re: testing for the existence of ballast resistor in my car
 

I believe that to be WRONG info. What I found in testing five different resistors is:
engine stopped (full current flowing continuously), voltage drop thru the resistor is right around 3.0 volt.

Re: testing for the existence of ballast resistor in my car
 

Exactly; unlike points there are no roadside fixes for a Pertronix; unless you keep a spare unit in the trunk.

Re: testing for the existence of ballast resistor in my car
 

My Pertronix quite on the road and I had a set of points and condenser with me to get me home. I did like the way it consistently ran until it stopped. If I go back to electronic, I'll bring another distributor all set set up with points and condenser.

Re: testing for the existence of ballast resistor in my car
 

I only run conventional points distributors in my old cars. NEVER have I even considered the possibility of carrying a spare distributor.