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butch49 · Dec 2, 2013

what should be the reading fromignition switch to positive side of coil in volts followed a wiring diagram and I have nothing on that side but 11 plus at negative side

David G · Dec 2, 2013

This would be indicate a 12V positive earth with a 12V coil and the points closed. I have no clue if that is what you have.

What are you trying to figure out?

butch49 · Dec 2, 2013

I have a 12 volt negative ground alternator, it is hooked 10 gauge from bat on alt, to negative on ammeter,where on the back of ammeter it has a neg sign,10 gauge to starter 12 gauge to neg, of ammeter to ignition switch. took out ballast resistor at moment from ign. to ballast to coil positive side. I have no voltage at plus side of coil.

Allan in NE · Dec 2, 2013

If you're measuring the primary, open the points. Otherwise, the circuit is going to ground and "shunting" your meter.

Allan

rvirgil_KS · Dec 2, 2013

With negative ground, the negative post on coil should go to distributor, positive post to ignition switch via resistor if used.

With switch on, approximate voltages at the coil should be:

Input (switch side) without resistor 12 volts, with resistor 12 volts points open, 6 volts points closed.

Output (distributor side) 12 volts points open, zero volts points closed

Sounds like the coil wires may not have been switched when alternator conversion was done.

pete 23 · Dec 2, 2013

Like others have said. If the points are closed and making good contact you will have zero voltage reading on the side of the coil that is hooked to the points. Electricity always takes the easiest path so it goes through points to ground. With points open you should read same as on input side of coil as there is no current flowing so no voltage drop. Now with a ballast resistor in the circuit , which you have to have if you have original coil or any 6 volt coil for that matter, you should read battery voltage at input to ballast, about 5 volts on coil side of ballast with points closed. You should also change your coil leads so the negative side of coil is going to the points when you have a negative grounded system.

mkirsch · Dec 3, 2013

Where are you placing the probes?

If you are touching the terminal on the switch and trying to measure at the coil, you will get 0 Volts.

You need to measure from the coil to ground, i.e. the tractor frame or the - battery post. Touch the red probe to the coil, then touch the black probe to the tractor frame.

Voltmeters measure voltage DROP. There is little to no voltage drop from the ignition switch to the coil. There IS voltage drop across the coil, so you get 11 Volts.

Owen Aaland · Dec 3, 2013

(quoted from post at 09:42:35 12/03/13) Where are you placing the probes?

If you are touching the terminal on the switch and trying to measure at the coil, you will get 0 Volts.

You need to measure from the coil to ground, i.e. the tractor frame or the - battery post. Touch the red probe to the coil, then touch the black probe to the tractor frame.

Voltmeters measure voltage DROP. There is little to no voltage drop from the ignition switch to the coil. There IS voltage drop across the coil, so you get 11 Volts.

There is no voltage drop in any circuit unless it is a complete circuit from positive to negative. The points make up the switch to open and close the circuit. With the points open there should be no voltage drop anyplace in the circuit. If there is a voltage drop across the coil with the points open then you have another path to ground other than the points. That may be a short in the coil, bad condenser, or short in the wiring between the coil and points.

gene bender · Dec 5, 2013

Red probe is positive so it would depend on which voltage and ground he is using as to the color of the probes.

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butch49

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David G

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butch49

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Allan in NE

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rvirgil_KS

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