Battery?

[Spudley]

Guys,
I inherited a '47 2N 12 volt conversion, 3 wire alternator, wired per JMOR's schematic that's
become a bit tricky to start. Had a farmer friend look at it and he said the "white box"
(resistor) was bad. He jumped the resistor and it fired up. After I replaced the resistor it now
cranks strong but will only start if I add a jumper battery. Then it fires up and purrs.
Is my battery junk, or has jumping the resistor messed up the coil?

 

[Bruce (VA)]

The resistor is likely limiting coil current because it's probably not needed at all, especially if you have a 12v coil.

See tip # 30.

All you need is the oem ballast resistor if you have a 12v coil.

Remove the white resistor. If your coil melts in a few hours of use, it was 6v; replace it w/ a 12v coil.

Or, measure the internal resistance of your coil; if it's 1 ohm or less, it's 6v. If it's 2 ohms or more, 12v.

And check your battery per tip # 49.
75 Tips

 

[Spudley]

Thanks Bruce, your 75 tips are most helpful. I'll check the battery. It just seems odd it cranks so well, yet won't start til I add another battery.

 

[Bruce (VA)]

Chances are it will start just fine if you remove the ceramic resistor.
75 Tips

 

[Geo-TH,In]

spudley,
When cars had points and condenser, they also used a ceramic resistor. When you turned the key to start it, the resistor is bypassed applying full voltage to the coil. Turn the key to run, resistor is no longer bypassed.

I came up with a way to bypass the resistor on my Jubilee during start and it fires off on the first or second crank because it's getting a hotter spark.

Some solenoids have a terminal you can use to bypass resistor. My Jubilee didn't have a the terminal for bypassing.

 

[Bruce (VA)]

If you would get a 12v coil for that Jubilee, you would not need any resistor. IC14SB NAPA coil.
75 Tips

 

[Tim PloughNman Daley]

In addition to what you've done and per Bruce(VA)'s 75 tips and JMOR's WIRING PICTOGRAMS, you should start with the basics and get the battery tested. Your trusty/local starter/alternator shop guy can bench test it on his test equipment for specific gravity as it must sustain a full charge under load. It is also important to buy a decent brand of battery (Interstate, Deka, Exide)and avoid bargain house units as they have poor lifespans and can be bad out the door. Do NOT buy a DEEP CYCLE battery -those are for boats and electric trolling motors, not cars and tractors. I'm not intending to offend your 'farmer friend' as I don't him, but make judgments based on facts, not just someone else's opinion. Did he test the resistor? Bruce and a few others once did a test on several different suppliers of these resistors and results showed their ratings were all over the place. Just because the package states "1.5 OHMS" does not guarantee it really is. Slap your VOLTMETER on it and test yourself. Also as stated, you only need the external in-line ceramic resistor on a 12-volt job when using a 6-Volt Coil. If you have a 12-volt coil, it is not needed. Test coils too -don't assume. Whether using a 6-volt coil or a 12-volt coil, you must use the original ballast resistor. When you say, "...it now cranks strong but will only start if I add a jumper battery..." -that should tell you something. You are stating it from the jumper battery, not the tractor battery. After it fires up and is running, what does the ammeter show? How long will the tractor stay running? Your starter shop can test the coil and resistors too.

Tim *PloughNman* Daley(MI)

 

[Geo-TH,In]

spudley,
Yes adding a 12v coil may solve your ballast problem. However there is a very good reason auto engineers bypassed the ballast when starting. A 12v battery only produces 12v without a load. When the starter is engaged, the voltage is less than 12v. In the winter it the batteries Cold cranking amps is much less. A weak battery the cranking voltage is less too. So bypassing the ballast and applying the full battery voltage, which will less than 12v, ensures a hotter spark even in the winter. After starting, the 12 volts is closer to 14v when the alternator wakes up.

Try shorting out your new ballast with a jumper wire. See if it starts without a second battery. Then remove the short and see if engine will continue running using new ceramic resistor.

50 years ago we would try hopping up the spark using high energy coils and larger condenser. All we accomplished was shorting the life of the points.

If you are electrically challenged, buy 12v coil and see if it work . Good luck.

 

[Bruce (VA)]

" So bypassing the ballast and applying the full battery voltage, which will less than 12v, ensures a hotter spark even in the winter. "

I gather from that comment that you are not familiar w/ the Ford OEM ballast resistor. It's .3 ohms cold, 1.7 ohms hot......unlike the fixed resistors in the old cars that needed bypassing.

This is an 8N tractor we're talking about, not a 57 Ford car.
75 Tips

 

[Geo-TH,In]

My Jubilee's ballast drops 6v and coil gets 6v when engine is not running, battery voltage is 12v. So lets say the battery is cold or weak and my cranking voltage is only 10v, then the ballast resistor uses 5 v and the coil only gets 5v producing a weak spark. By bypassing the ballast, the coil will get the full 10v. Guess what, a hotter spark!

The auto engineers figured this out over 50 years ago. Tractors that came from the factory with 12v bypassed the ballast. Some used a special terminal on the solenoid.

This isn't something new, been done for years. Perhaps you should add this to your 75 tips.

 

[Bruce (VA)]

You are entirely missing the point.

The Ford tractor came out in 1939 with a VARIABLE ballast resistor. It did not need to be bypassed.

When it was cold, the resistance was .3 ohms.

When the tractor was running, the resistor got hot and increased to 1.7 ohms.

So, at 6 volts starting voltage, .3 ohms on the resistor and 1 ohm on the coil, starting current was nearly 5 amps.

You are using a fixed ballast resistor on your tractor.

What's the point? What's wrong w/ just putting a 12v coil in it and not worrying about a resistor that needs to be jumped?

I think my comment in tip # 30 covers the point fairly well: " If you are doing a 12-volt conversion, it's easier to use a "12-volt" coil. "

Yea, I'm familiar with the resistors on the old cars; been working on them since the early 1960's. And currently drive a 29 Ford.
75 Tips

 

[Geo-TH,In]

I'm confused, Why would anyone converting to 12v use a ballast designed for a 1939 N, 6v? My jubilee 12v conversion used the newer fixed ceramic resistor.

BTW, All ceramic ballasts are wire wound. All wire resistors increase resistance with increase in temp.

When I was in HS in the mid 60's, I had a 65 cuda. I carried a spare ballast resistor in glove box. It was a no brainer when car would start and instantly die when the key went to the run position it was time to change the ballast.

I sometimes reminisce of all the old cars I've had. My favorite and best looker was a 1962 XKE. None compare to a 2018 XT5 Luxury. Best car so far.

 

[Bruce (VA)]

" I'm confused, Why would anyone converting to 12v use a ballast designed for a 1939 N, 6v? "

That resistor was used on all N's from 1939 to 1950 because of the front coil. Because of it's design and materials used, it would melt at a running current greater than 4 amps. It was cheaper for Ford to use the oem ballast resistor at ,3 ohms cold and 1.7 ohms hot than to design a bypass switch.

Even with a 12v square coil, the oem ballast resistor is needed because the internal resistance of the 12v coil is about 2 to 2.25 ohms.

Using a 6v round coil on 12v with the ceramic resistor will work fine IF you get a resistor of the correct value.

What is the resistance of the resistor on your tractor cold & hot? Don't take the makers word for it; the values can range from 1 to 3 ohms regardless of what the label says.

But again, why go through the time & expense to install a resistor w/ a bypass when the 12v NAPA IC14SB coil will work perfectly well on your tractor?


A 65 Cuda in HS? That sounds nice; I drove a 47 Chevy. When it ran......
75 Tips

 

[FordNMan]

if the coil was messed up it probs wouldnt run right. Get your battery load tested. Youd be surprised by the amiunt of issues a bad battery would cause

 

[Geo-TH,In]

An ohmmeter isn't very accurate. All I can say is cold, the resistance of my ballast is the same as the coil and the coil current is 4 amps. When you have two resistors are in series and they both have he same voltage drop, they both have the same resistance. So in theory, 12v, 4 amps = 3 ohms total.
Therefore the ballast and coil both have 1.5 ohms. Shorting out the ballast will produce 8 amps in the coil, in theory. However the cranking volts will be less so amps will be less too.

I use my Jubilee and a 6 ft woods finish mower to mow about 4 acres. Love the ride over any lawn mower. Love how fast it cuts the lawn too.

 

[HFJ]

[b:879b7e7c24]"[i:879b7e7c24]A cheap[/i:879b7e7c24] ohmmeter isn't very accurate."[/b:879b7e7c24]

fixed that for u i have a handful of meters. most of them are as u describe, but i trust the numbers my Fluke tells me.

 

[Spudley]

Thanks Bruce. I ordered and installed a 12 volt coil and she fired up without a helper battery. Appreciate all the replies.