1939 Ford Ballast Resistor

[Ryan]

Hey fellas, check this out:



That there is a stock 1939 Ford ballast resistor. Anyone know what ohm it is? 1.5?

[ken ct]

Why do you need its ohm rating?? just use it. either it works or dosen't.Should cut voltage down to coil to 3-4 V. at the coil. ken ct.

[Ryan]

Originally Posted by ken ct

Why do you need its ohm rating?? just use it. either it works or dosen't.Should cut voltage down to coil to 3-4 V. at the coil. ken ct.

I'm protecting my new Bubba's Hot Rod Ignition... And I'm curious. Anyone know?

[Hoop]

Check ohms with a meter ... basic function for just about any multi-meter.

Regardless of what somebody told me, I'd still read it for myself.

(Bubba ... Jim ... is a heck of a guy and a terrific resource to Ford Barn.)

[Ryan]

Originally Posted by Hoop

Check ohms with a meter ... basic function for just about any multi-meter.

Regardless of what somebody told me, I'd still read it for myself.

(Bubba ... Jim ... is a heck of a guy and a terrific resource to Ford Barn.)

I'm an idiot... I guess that's why they call it in Ohm meter, huh?

[Bruce Lancaster]

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NAPA lists it as having .35 ohms resistance, but I'd like to dig up a Ford source on that. NAPA version, I think still available, is ICR 40...
Try to check resistance 2 ways, across the actual terminals and across the resistance coil itself...somethimes thay develop extra resistance where they crimp in the little wire.
What coil are you using? If not original, is this particular resistor appropriate? There are lots of different values out there.

[Hoop]

"I'm an idiot... I guess that's why they call it in Ohm meter, huh?"

Why do you think I praised Bubba? Had to ask him a basically dumb question today myself.

By the way, I can absolutely guarantee you that the wrong resistor can cause your coil to EXPLODE.

Twice.

You'd be an idiot if you didn't ask.

[Ryan]

Originally Posted by Bruce Lancaster

NAPA lists it as having .35 ohms resistance, but I'd like to dig up a Ford source on that. NAPA version, I think still available, is ICR 40...
Try to check resistance 2 ways, across the actual terminals and across the resistance coil itself...somethimes thay develop extra resistance where they crimp in the little wire.
What coil are you using? If not original, is this particular resistor appropriate? There are lots of different values out there.

I just measured it at .5. I need 1.5, but bubba sent me one... So I'm all good.

[Bruce Lancaster]

On any custom setup, either carry a spare or write down make and model of something that uses the resistor as OEM as well as the rating.
I've been hunting catalogs, and NAPA Echlin and Standard, the 2 brands you can count on finding in Resume Speed, Montana, list the ratings of only about half the resistors they carry! All the listed ones are above or below your 1.5, naturally.
If yours gets smoked, Lord help you if you are faced with an 18 year old counterman and have no specific car as the source...

[tdlmomowers]

Yeah I know, Some of these kids that the parts stores have working for them couldn't find their butt with both hands and a flashlight. They are way too dependent on the computer catalog and don't know how to use the paper catalogs. They have grown up in the electronic age and don't even know what a set of points does in the ignition system.

[Terry,OH]

0.5 Ohm is correct.

[Ryan]

So this is odd... I tossed the stock resistor, replaced it with a new 1.5 ohm resistor and then fired the car up. The resistor had white smoke trickling out... I got scared, took it out and put the stock one back in - no smoke.

Weird.

[Bruce Lancaster]

Resistor is a hot part...it is likely just burning off some sort of residue from manufacture.
It will stop smoking in a couple of minutes...or if something is wrong with it, burn out.
More likely the former!

[BUBBAS IGNITION]

Originally Posted by Ryan

So this is odd... I tossed the stock resistor, replaced it with a new 1.5 ohm resistor and then fired the car up. The resistor had white smoke trickling out... I got scared, took it out and put the stock one back in - no smoke.

Weird.

Happens all the time , the smoke is normal on a new resistor . Some kind of coating on the unit i believe. I guess i should put a warning on the box. Run it as is .

[ken ct]

All new resisters like that smoke a little for a minute or 2. Bubbers right. Its normal. ken ct.

[Ryan]

It smoked instantly... That's cool? It didn't feel warm to the touch really.

[John Kennedy]

They usually get too hot to the touch. Also, resistance goes up when it gets warm.

[Dick Webber]

I tried 2 different NAPA resistors (ICR 40) and both smoked and cut voltage down to 2 volts. Not enough to run the engine. This is with the stock 39 helmet distributor and coil, but before I had the coil rebuilt.

[FlatheadTed]

Volts divided by Amperes = Ohms .Eg 6volts divided by 4 amps = 1,1/2 ,

[John Kennedy]

So on a 6 volt car, you still need a ballast resistor? I thought they ran the full 6v thru the coil.

Also, any ballast won't protect the distributor, but the condenser protects the points.

[Hoop]

"So on a 6 volt car, you still need a ballast resistor? I thought they ran the full 6v thru the coil."

(Nobody cleared this up so I'll keep it going.)

The original system used a ballast resistor. Sending 6V to a stock coil is too much. Keep in mind that when the engine is running, you may be making more than 6V.

The internal resistance (ohms) of the coil is added to the ballast resistor (ohms) to reduce the amps to spec. Volts divided by ohms equals amps ... Volts divided by amps equals ohms, either way.

It's a good idea to verify with a meter the resistance in the coil and that of the ballast resistor.

Stock resistors such as Ryan's have a cold value and a hot value. (!!!!!) Less resistance when the engine is cold helps overcome the current draw of the starter ... when the resistor heats up, the amps to the coil are reduced, and the coil is protected from overheating.

That's the basics, but it's a good practice to keep a decent meter nearby and double-check what you're working with.

[John Kennedy]

Good to know Hoop, thanks. Is that you in that avatar?

[Bruce Lancaster]

All flatheads '32-48 used the resistor...A and B and the '49-53 engines used straight 6V.
And the resistors do get warm...you can actually see and feel your fingers smoking if you touch the element. If you hear screaming, you have gotten your fingers to the right place.

[Kentf1003]

I measured mine at .5 ohm. I also read that somewhere. For what it's worth.

[fordy_nine]

You cannot accurately measure the resistance of a power wirewound resistor with an ohmmeter using a few milliamps of current. Well, you can measure it, but it is not relevant to its actual use. The resistor needs to be under actual circuit load which, in this case, is a few amps. The resistor must be at normal operating temperature which increases its resistance......Bob L

[TomT/Williamsburg]

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Originally Posted by Bruce Lancaster

All flatheads '32-48 used the resistor...A and B and the '49-53 engines used straight 6V.
And the resistors do get warm...you can actually see and feel your fingers smoking if you touch the element. If you hear screaming, you have gotten your fingers to the right place.

Bruce, you are one funny dude!

[Ken/Alabama]

Originally Posted by tdlmomowers

Yeah I know, Some of these kids that the parts stores have working for them couldn't find their butt with both hands and a flashlight. They are way too dependent on the computer catalog and don't know how to use the paper catalogs. They have grown up in the electronic age and don't even know what a set of points does in the ignition system.

Funny you said that. About 2 yrs ago I was in a local parts store and asked for a set of ignition points and the kid behind the counter gave me the deer in the headlights look,he had absolutely no idea what I was talking about.