farmall m 12volt at points

i cinverted my farmall m tractor to a 12volt system last year with a kit that came from yt. this kit came with a voltage regulator to bring it from 12 volts down to 6 volts at the points what do i need to do to get rid of the voltage reducer and have 12 volt coming out of the points

Not sure what you've got for a kit.

Test your voltage at the primary wire running from the switch into the coil. If you've got 12v there AND at the points, you need one of two things, but not both. You can put a ballast resistor inline in the wire, between the switch and the coil, to drop the voltage to 6. The other way to do it is to get a coil for a 12v system that has the resistance built in.

Any good counterman at an autoparts should be able to fix you up with either.

I misread your question, and now see from the post above that you are talking about the resistor I mentioned.

Short answer is that you don't want 12v going to your points. They are designed to take 6v. Even the standard 12v automotive systems that used points stepped the voltage down to 6v before going to the coil and points.

Chrysler, especially, but others, too, used to use a two-sided resistor wired up so that it fed 12v to the coil only while cranking but switched back to 6v once the motor was running. Worked fine, but it was common to replace that resitor when one side burned out. Point is that even with that setup, you didn't feed a steay diet of 12v to your points -- it will only burn them up faster.

Leave that resistor right where it is.

If you get a 12 volt coil make sure it has the resistance built in, it should say on the coil.
Some coils are marked 12 volt but still need a external resistor.

I am not trying to argue but I am pretty sure the resistor has more to due with the dwell time of the coil than it does wih saving the points. The problem arose from the coil becoming "overcharged" and therefore overheated by a log dwell time at idle especially with 4 cylinder engines where there was more time between each ignition event. The problem was still apparent in 6 cyl and 8 cyl engines but it was most pronounced in 4 cyl applications. To solve the problem, it was much easier to just cut the voltage down from 12 to 6 to reduce the "overcharge" effect of a long dwell time. I always hear people talk about burning points up faster with 12v systems, but it's not the points you should be worried about, it is your coil that is really taking the abuse, especially with low RPM tractor engines. And really there is no need for 12v on a tractor system that was designed for 6v, there is more than enough dwell time to recharge the coil on these old engines, it would be different if they were turning 6K RPMS but most are turning less than 2,000 so running 12v to your coil (except when a 12v coil is used) is just wearing your coil out faster, and making it perform worse than what it would at 6v due to the increased heat. If no one believes me that is fine too, I am sure there is someone out there who has been running for years with a 6v coil at 12v with no resistor.

Simply get a true 12 Volt coil. (12 Volts no external resistor required) NAPA IC14SB is a common choice. Install it and remove the resistor. If your system is positive ground the + terminal of coil goes to distributor. If the system is negative ground the - terminal of the coil goes to distributor. The points don't care if they are in a 6 volt or 12 volt system.

Voltage seen at the coil depends on whether points are open or closed. Here's a link to a chart that may help explain that.

Bob
Ignition Circuit Test Voltages

Nothin' there to apologize about. Sounds like we're all pretty much on the same page, and I like your description of the effect of the dwell time issue.

It all makes good sense, and just as you say, 12v into a coil without the internal resistor is hard on the coil, both in terms of performane and durability. I'd just add I think it's hard on the points and the condenser, too. The points are nothing but a switch and are, in theory indifferent as to what the voltage is (at least within the reasonable range for the size of the contacts and the gap, but the condenser especially is designed to absorb the shock on the primary circuit when the field collapses, and that shock is a lot heavier when the coil is "overcharged" leading to burned points and smoked condensers.

So pick the part that would be more apt to fail, I just would advise against running 12v into a coil that wasn't built to step it down to 6.

With the points open you will read battery voltage with the points closed and if you have a ballast resister in place you will read the 6 volts you need or very close to the 6 volts. With the points open you have an open circuit so the meter will read true battery volts
Hobby farm

IFFFFFFF you wanan get rid of any ballast resistor on a 12 volt tractor YOU NEED A FULL TRUE (some call internally ballasted) 12 VOLT COIL

Whether or not a voltage dropping (12 to 6) external series ballast resistor is needed or not DEPENDS ON WHAT COIL YOU HAVE. If its a 12 volt tractor but a 6 volt coil, THE RESISTOR IS NEEDED otherwise the coil overheats.

A 12 volt tractor needs EITHER a full true 12 volt (some call internally ballasted) coil NO BALLAST REQUIRED or elseeeeeeeee if its a 6 volt coil then you need the external series voltage dropping (12 to 6) ballast resistor so the coil dont draw too much current n overheat

ALSO Id Pertronix recommends the ballast THEN YOU INDEED NEED IT cuz depending on the elec switches current rating it may still be required (Thats if you have an elec switch???)

The voltage on the coils low output (to distributor) terminal should read near full battery voltage when the points are open, but near ZERO volts when they are closed. Over on the coils input (from IGN switch) the voltage should be 12 volts on a straight 12 volt system with a 12 volt coil or 6 volts if a 6 volt coil and ballast is used WHEN THE POINTS ARE CLOSED.

Get it????????????

John T

In a 6 volt system when the points close current flows through the points, coil, and switch, to the battery. The issue is amount of current flow. The circuit (points and coil) is designed for a maximum of 3 to 4 amps of current.

When battery is increased to 12 volts the 6 volts is doubled and so is the current, exceeding the design of coil and points. Excess current will soon destroy both. A ballast resistor approximately equal to the resistance of the coil primary can be added in series between coil and battery. This drops 6 volts across the coil and 6 volts across the resistor maintaining the 3 to 4 amps of current.

Or with 12 volts, a true 12 volt coil (primary of coil wound for 12 volts rather than 6 such as NAPA IC14SB)can be used without the need for a resistor. It's internal resistance limits the 12 volt system to 3 to 4 amps.

With current held within design limits the points and condenser will work with either 6 or 12 volt supply.

The current flowing in the circuit is governed by voltage and resistance, the dwell time is irrelevant.

(quoted from post at 15:51:21 05/02/09) In a 6 volt system when the points close current flows through the points, coil, and switch, to the battery. The issue is amount of current flow. The circuit (points and coil) is designed for a maximum of 3 to 4 amps of current.

When battery is increased to 12 volts the 6 volts is doubled and so is the current, exceeding the design of coil and points. Excess current will soon destroy both. A ballast resistor approximately equal to the resistance of the coil primary can be added in series between coil and battery. This drops 6 volts across the coil and 6 volts across the resistor maintaining the 3 to 4 amps of current.

Or with 12 volts, a true 12 volt coil (primary of coil wound for 12 volts rather than 6 such as NAPA IC14SB)can be used without the need for a resistor. It's internal resistance limits the 12 volt system to 3 to 4 amps.

With current held within design limits the points and condenser will work with either 6 or 12 volt supply.

The current flowing in the circuit is governed by voltage and resistance, the dwell time is irrelevant.

Click to expand...

I would like to add that Dwell time is not irrelevant, as stated with 12v going to a 6v coil the dwell time is more than needed therefore leading to a heating of the coil and therefore shortening it's life, there are two options to fix this
1. Shorten the dwell time, not that easy on an old non electronically controlled system OR:
2. Add resistance to the system therfore reducing voltage and amperage back down to a safe level because we all know that Current = Voltage Divided by Resistance and also Voltage = Current multiplied by Resistance.

If you could cut the dwell time in half then the system would be perfectly happy at 12v with no resister.