12 volt to 6 volt resistor

Anonymous-0 · Mar 7, 2010

I placed a new resistor on my b farmall that allows the current from a 12 volt battery to be reduced to a 6 volt coil. When using a test light the light is bright on the wire (posts) of the resisitor where the current comes in and is dimmer on the wire (posts) where the current goes out into the coil.

Question 1-Should the outcoming electrical current be dimmmer

Question 2-Are resistors poloarized or can they be hooked up either way.

ALSO
When I was trying to start the tractor I have apparently blown out the starter switch and the resistor was very hot.

Jon Hagen · Mar 7, 2010

Yes, with the ignition points closed, the coil side of the resistor should be dimmer than the ignition switch side.

No the resistor does not care which direction current flows through it.

It is normal for the resistor to run hot, very hot when the points are closed and engine not running.

With a DC voltmeter, you should see near 12V in and 6-7V out to the coil.

John B. · Mar 7, 2010

With the points closed and the ignition on the test light will not light up. All the current will be going to ground thru the points which is an easier path for the electricity to travel. I don"t mean to critisize your post but this may be helpful for farmallbee to know this.

John T · Mar 7, 2010

Just to set the record straight, its CURRENT "THROUGH" the ballast resistor (from ign switch, to and through resistor, to and through coil, to and through closed distributor points to ground) that causes VOLTAGE DROP "ACROSS" IT....

Sooooooo, if theres 12 volts at a typical ballast resistors input and the points are good and closed, the current through it will cause a 6 volt drop "across" it leaving 6 volts at the input of a 6 volt coil (as it was designed for).

If you place a voltmeter with one lead to frame ground and with the ignition on and if points are closed, there should be near 12 volts on the input of the ballast,,,,,,,6 volts on the output (to coil),,,,,and near zero volts on the coils output since points are closed.......

Thet are pure passive resistive devices NOT POLARITY SENSITIVE

John T

Jon Hagen · Mar 8, 2010

John B, I think we are close to on the same page.

On a 12V system with a ballast resistor,with the ignition on and the points closed, Voltage on the primary coil to distributor lead should read 0 volts as you say. the lead from the output of the resistor to the input of the coil should read near 6V and the ignition switch side of the resistor should read 12V.

As John T says, a resistor only drops voltage when their is a load on it. If the ignition points are open, their is no load and the entire ignition primary system will read 12V, thats why it is important to have the points closed when measuring voltage at various points in the ignition system.

barn E · Mar 8, 2010

Nother thing if I recall, voltage drop depends on the resistance of the load. So coil and resistor sorta have to match for current to be right and not burn points or give weak spark. Dave

12 volt to 6 volt resistor

Anonymous-0

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Jon Hagen

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John B.

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John T

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Jon Hagen

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barn E

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