Is this a 1.5 ohm ballast resistor?

I recently ordered a 1.5 ohm ballast off amazon.



I made a simple test circuit.
If you notice the HF meter on the left is measuring the voltage across the resistor.

The HF meter on the right is measuring the current going through the resistor.

Is this a 1.5 ohm resistor??

The resistor is on its way back to Amazon.
I love amazon. Free return shipping.
I'll refund within a few hours after UPS prints the shipping label..

I should be getting a 1.5 ohm resistor Dec 23.

I will be testing it to make sure the new ballast is what Amazon claims it to be, 1.5 ohms..

If you replace a ballast resistor do you test it before using it?

If you swap meters do you get the same results?

If this simple circuit was connected (you really need to show us in an image, or diagram what you are connecting to what) from a 12v battery at 12.6 volts, and it is the only thing in the circuit, it is no wonder it shows what you call wrong readings. It should be connected to a 1.5 ohm coil primary, or another 1.5 ohm resistor in series. What was its Ohm reading? Jim

I have no way to calibrate the cheapie HF meters.
There are no adjustments if I wanted to make them
So I put all my meters in series and all measured the same amps
within + or - .02 amps.
Did the same with voltmeters. 2 voltmeters were way out of the
ball park, those I removed the 9v battery and used a sharpie and
wrote junk on them. The good voltmeters were within + or - .03 v

No
Those pictured are HF multi meters.

Ohm's law applies to all resistors.
All you need to calculate ohms is the volts across the resistor and the current through the resistor. JohnT our EE can confirm this. As long as the I squared R doesn't exceed the watts of the resistor, Ohm's law will apply.
That's all I'm giving you to calculate the ohms.

Knowing how I built my test circuit is irrelevant.

Picky, Picky.
Can you see the meter on the left is measuring volts?
Can you see the meter on the right is measuring amps.
Please answer the question, what are the ohms of the resistor?

(quoted from post at 17:25:27 12/17/22) Picky, Picky.
Can you see the meter on the left is measuring volts?
Can you see the meter on the right is measuring amps.
Please answer the question, what are the ohms of the resistor?

Click to expand...

IF the voltage applied is 4.87vdc
IF the current is 5.43 amps
THEN the resistance is .89689245 ohms

AND remember than an englishman's 'OUSE is his 'OHM

But why not just use the multimeter to measure the resistance to find the value of the resistor?

Geo,

Do you have access to 1000 foot spool of 12awg copper?

D.

Ballast resistors change resistance when in use. The colder they are the less resistance. Carbon (electronic) resistors are measurable because they are intended for use in systems that never heat them. The applied voltage is not a real circuit analysis. The about 4 amp draw of a typical ignition circuit is with the points closed. The service load applied is somewhat less than 50% (POINTS OPEN) Thus, my opinion is that the answer makes sense, but is not your tractor operating. Jim

Do you understand ballast resistors? A ballast resistor changes resistance from cold to hot? It will not measure 1.5 ohms until it is hot. So if you are measuring a cold resistor you, you have inaccurately assumed the ballast resistor is bad.

Those meters are inaccurate how do you plan to resolve that.

Exactly, resistance is equal to voltage divided by current.

George, I've long since lost track of what it is you're trying to accomplish. Are you thinking that if you can just find the Perfect Ballast Resistor, your Jube will achieve Spark Nirvana and finally, at 70 years of age, realize its full potential?

The Kettering ignition system is a big Kompromise with a Kapital K. When you fire it up with a fresh set of points, the points quickly burn adding resistance to the circuit and mucking up your calculations. The ballast resistor just isn't that important. If you want a tractor that starts up reliably in any sort of weather, switch it over to Pertronix. Otherwise, slap the thing back together and call it good.

what is the voltage in and then what is the voltage out who cares about the OHMs

Mornin good neighbor YET ANOTHER SIMPLE BALLAST AND OHMS LAW QUESTION I SEE ????? Will this one yield an entire page of discussion like the other ??????? Fun, so very simple (how can something so simple R = V/I be soooooooo confusing????) yet still an interesting question. You did good George I hope this answers and settles all your concerns

Thanks for the vote of confidence Georger, AND AS YOU ALREADY KNOW YOU ARE CORRECT WHEN YOU STATE

All you need to calculate ohms is the volts across the resistor and the current through the resistor. JohnT our EE can confirm this

Iffffffffffff the meters are accurate ?? Yes YOU ARE CORRECT R = V/I = 4.87/5.43 = 0.896 Ohms

You further ask ????????? Is this a 1.5 ohm resistor?? The simple accurate answer ifffffffffffffffff the meters are accurate is a definite NOOOOOOOOOOOOOOOOOOOO, as 4.87/5.43 only equals 0.896 Ohms !!!!

NOTICE TO ALL:

DEFINITION: A thermistor is a type of resistor whose resistance is strongly dependent on temperature, more so than in standard resistors

There seems to be some confusion below in how old car coils with true actual internal THERMISTORS functioned VERSUS old tractor coils that used 6 volt coils on 12 volt tractors which, therefore, required a voltage dropping (12 down to 6) ballast RESISTOR NOTE I said RESISTOR NOTTTTTTTTTTTTT THERMISTOR

Those old car coils with internal THERMISTORS were NOT used to drop 12 battery volts down to 6 for 6 volt coils on 12 volt autos, the THERMISTORS were lower resistance when cold (for better starting spark energy PLUS different engine RPM as the picture explains) PLUS but higher resistance after warm up THATS NOTTTTTTTTTTT THE SAME FOR MODERN BALLAST RESISTORS (they are NOT Thermistors) They can be equipped with a ballast by pass when starting to improve cold weather starting but the external ballast resistors (drop 12 to 6) ARE NOT THERMISTORS

Before anyone has a calf or sets their hair on fire YESSSSSSSS I know resistance changes with temperature but what Im telling you is modern voltage dropping ballast resistors like old tractors use ARE NOT THERMISTORS that serve the purpose of old car coils (temp compensation and RPM effects). If they are 1.5 Ohms they stay fairly close to 1.5 from cold to hot UNLIKE old car coils with internal temp compensating THERMISTORS

On a 12 volt tractor you can use EITHER a full true 12 volt rated coil (around 3 ohms, some 2.5 to under 4) orrrrrrrrrrrrrr a 6 Volt rated coil (around 1.5 or so Ohms). They limit coil current to around 4 amps so points dont burn up quick For 12 volts if you had a 50 50 voltage divider to drop 6 across ballast and 6 coil if the coil were 1.5 ohms the ballast would be the same 1.5 Ohms. I (past used tractor dealer and farmer) have seen ballast in the 1.3 to 1.8 or so ohms range again they are NOT nor used like old car coil temp compensating THERMISTORS

There ya go George, if you want to use a full true 12 volt rated coil fine or if you want a 6 volt coil PLUS an external voltage dropping (12 to 6) RESISTOR fine, dont let anyone talk you out of it its YOUR choice.

THERMISTOR (old car coils) IS NOTTTTTTTTTTTTTTTT SAME AS AN OLD TRACTOR BALLAST RESISTOR

DISCLAIMER I believe all the above to be true but NOOOOOOOOOOOO warranty. Everyone is entitled to THEIR opinion this is mine and I hope this helps explain the difference in old car coil internal THERMISTORS versus the 1.5 Ohms Ballast RESISTORS like George asked about. They are NOT the same they serve different purposes

YES unless Ohms law changed, V = R I R = V/I 4.87/5.43 = 0.896 Ohms

NOOOOOOOOO warranty but I believe this is accurate regarding old car THERMISTOR equipped internal and old tractor external Ballast (drop 12 to 6 volts) RESISTORS

Best wishes to all and to all I wish you and yours a very Merry CHRISTmas

John T At a Cracker Barrell north of Dade City Florida

Some meters have junk written on them. Can't fix them.
Some HF meters are surprisingly accurate measuring AC and DC
volts and up to 10 amps.
I've yet to find an ohmmeter worth a crap.
I have a dual ballast used on my old dodge aspen wagon.
It has two resistors in one ceramic casing.
This may have been mopar first attempt at electronic ignition.

Do you know the resistance or each is?

George, I've long since lost track of what it is you're trying to accomplish.

Mark, you mean I have to have a reason for doing things? lol

My son wants to learn everything about my Jubilee.
I bought the Jubilee with a rebuilt engine. It is a good tractor and will last him a lifetime.

It was converted to 12v before I bought it.
The wiring was a mess, so I got rid of the old wiring and made my own wiring harness. I used the old ballast and the 6v coil.

My goal is to find exact replacement ballasts and 6v coil, which isn't as easy as you would think. A 1.5 ohm ballast was .9 ohms and the current was 6 amps. No wonder points don't last if you don't have a way to verify what you are buying.

Using my test setup, I'll easily find a replacement coil and ballast. I may even try to use a larger ballast and reduce the primary current.
My test setup is very simple. Two resistors the same size, same ohms, in series is a voltage divider. If I put two 6v coils in series, each will have the same voltage. If I put 2 ballast resistors the same size in series I will have a voltage divider. Each will have the same voltage. It's that simple. I don't need precision voltmeters or ammeters.

Many YT members have no idea that ohmmeters are crap.
Some couldn't tell me my 1.5 ohm resistor was .9 ohms.

Do you have an ohmmeter that can accurately measure 1.5 and .9 ohms?

Mark, I'm a full time retired physics, math, and electronic teacher. One has to have a little fun playing with simple series circuits.
What do you do for fun in Florida?

If it us a 12 volt system, why not buy a 12 volt coil?

(quoted from post at 19:29:45 12/18/22) Some meters have junk written on them. Can't fix them.
Some HF meters are surprisingly accurate measuring AC and DC
volts and up to 10 amps.
I've yet to find an ohmmeter worth a crap.
I have a dual ballast used on my old dodge aspen wagon.
It has two resistors in one ceramic casing.
This may have been mopar first attempt at electronic ignition.

Do you know the resistance or each is?

Click to expand...

First I have never said one bad word about your post. I know you don't like to be questioned. You know those meters are junk how could you continuously trust any of them.

I have a $40 meter from HF that was gave to me and a few other free meters they are just not accurate no way I could trust them.


Yes, and I would not use a HF meter to check it : )

If I were working on your lo-boy truck what would you think if I used a HF meter to check a circuit.

The good out of all of this is the education so its not all a write off. Most still love ya Merry Christmas maybe Santa will deliver a good meter to ya.

George, To your question, is this a 1.5 ohm resistor? No, not for your application. However, the resistance changes with temperature and the test conditions are not stated. It would have been interesting to increase the voltage drop across the resistor and see if it would show 1.5 ohms before melting.

Do I test ballast resistors before installation? Yes, I have however, I find the measurement many times is not in agreement with the label.

I suggest checking the primary circuit current with the tractor operating and at temperature. If the amp draw is between 3 and 4 amps...take full credit for your skill.

Good luck with finding a ballast resistor that matches the label.

However, the resistance changes with temperature and the test
conditions are not stated.


That is true. A wire ballast resistor increases resistance as it
heats up, so my 0.9 ohm ballast may be slightly less ohm.
Cool off wires if you want a super conductor.

Thermistors are the opposite. Temp increases resistance
decreases.

As far as test conditions what more do you need than voltage and
amps? Everything else is just a distraction.

What would be a good battery one can use as a standard voltage?
When I calibrated meters at Crane naval base we had a voltage
standard source.
What do you use to calibrate or check your meters?
All meters used at the USNAD base were calibrated every 6
months..

(quoted from post at 22:21:01 12/18/22) What would be a good battery one can use as a standard voltage?
When I calibrated meters at Crane naval base we had a voltage
standard source.
What do you use to calibrate or check your meters?
All meters used at the USNAD base were calibrated every 6
months..

Click to expand...

I have 3 high end meter/scope/DSO I make sure they are all with end 1/10 of a volt of each other. From there I check all my other DVOM if they are wacky then they go in the wacky drawer. That wacky drawer you should hide your HF meters in : ) File 13

EXCELLENT SOURCE OF INFORMATION Thanks for posting, a pictures worth a thousand words

Those show what I described in another thread as THERMISTORS versus RESISTORS. The first is a RESISTOR
for use with ballast by pass equipped tractors (like on all old tractors I saw) ,,,,,,,, while the other
is a THERMISTOR when theres no ballast by pass like some old car coils used (didnt see any on old
tractors)

Thanks again great help

John T

JohmT
Back in the day of TV tubes.
The heaters inside of the tubes were wired in series.
The heater inside the tube, when cold, had very little resistance. As they got red hot the resistance grew.
To prevent large surge current when you turned on the TV, there was a large thermistor placed in series with all the heater elements.
The thermistor almost looked like a power resistor.
It was common for the thermistor to go bad and it was easy to replace. The thermistor prevented a large surge current when the TV was first turned on.

(quoted from post at 16:30:14 12/18/22) JohmT
Back in the day of TV tubes.
The heaters inside of the tubes were wired in series.
The heater inside the tube, when cold, had very little resistance. As they got red hot the resistance grew.
To prevent large surge current when you turned on the TV, there was a large thermistor placed in series with all the heater elements.
The thermistor almost looked like a power resistor.
It was common for the thermistor to go bad and it was easy to replace. The thermistor prevented a large surge current when the TV was first turned on.

Click to expand...

ere ya are Geo. & I do not know the years used.

Looks like some of the old Chrysler products ignitions with the dual ballast but thats OLD memory cells
workin lol

John T

Thanks,
I found my dodge compensating resistor I carried in my aspen
wagon is 1.25 ohms.
Your diagram is showing 0.5 ohms.
If I put the 1.25 ohm resistor in series with my new 6v coil,
the primary current is close to 5 amps.
The Amazon ballast was supposed to be 1.5 ohms, turned out to be
.9 ohms. That ballast in series with the new 6v coil drew 6 amps
and got very hot very fast.

Something is rattling in my brain thinking the primary current
for a 6v coil was closer to 4 amps.

I need to do more testing.
I will be posting my results..

(quoted from post at 19:38:18 12/18/22) Thanks,
I found my dodge compensating resistor I carried in my aspen
wagon is 1.25 ohms.
Your diagram is showing 0.5 ohms.
If I put the 1.25 ohm resistor in series with my new 6v coil,
the primary current is close to 5 amps.
The Amazon ballast was supposed to be 1.5 ohms, turned out to be
.9 ohms. That ballast in series with the new 6v coil drew 6 amps
and got very hot very fast.

Something is rattling in my brain thinking the primary current
for a 6v coil was closer to 4 amps.

I need to do more testing.
I will be posting my results..

Click to expand...

hose resistances are from a SS Ign book published before Dodge Aspen was made.

I have measure coil currents on many cars, trucks, tractors and they fall between~3.5A and 4 to 5A occasionally. Steady 'on' measurements can only be made with engine not running, when battery voltage will be close to either 12.5 or 6.3 and remember that when running battery will be closer to 14.5 or 7.3