Does this sound right about a coil and resistance?

[wire2]

Re: Does this sound right about a coil and resistance?

i think there should still be a drop. you don't need current in the circuit to measure voltage (except for what the voltmeter draws).

No. Ohm's law will prove it. Without current, there is no voltage drop.

Compare it to a garden hose with the tap just barely on, assume city pressure of 50 psi. If the nozzle is not opened, the pressure at the nozzle will be 50 psi within a few seconds. If you kink the hose (but not completely sealed) the nozzle pressure will still be at 50. Thats comparable to 2 resisters in a circuit.

Until you open the nozzle, and have flow (current) Now there will be a drop in pressure. (voltage)

A good Fluke VOM has 11 Megohms input resistance, so the load presented is negligible.

EDIT

It occured to me, some people are not familiar with Ohm's law. Briefly;
It states that E = I/R. where E is voltage (Electromotive force), I is current, and R is resistance.
If you measure across a resistor in a circuit with no current, and say, a 1,000 Ω resistor, it becomes E = 0/1000. Zero divided by 1000 is still zero, and E is also zero (the voltage across the resistor). There can be 12 volts, or 100 volts dc on the circuit, it makes no difference.

 

[ChriKa]

Re: Does this sound right about a coil and resistance?

I'm not much of a sea dog as rolling cages with lots of horses is more of what I do.
If this is a point system with a ballast ( and it was a chrysler ) when the ballast went the motor would run in the STARTer position until you let go of the key. Overly Hot coils .... juice.... have you
1) check the spark at the plugs by removing the plug wire and grounding it to the engine block. Yellow is weak and Blue is peak.
2) is a question , with the points do you have a condenser in the distributor?? I would say you should have . Condensers burn points , ballast restricts voltage, coils magnify the voltage provided from the ballast to the condenser to the points and when the points open u get spark.
3) In the past on autos I found that coils burn out typically when there is a short coming off the (-) side of the coil
4) Wish I knew more about boats as I've never replaced the hoses to a merc outdrives trim, the down hose
Good sailing.!

 

[nola mike]

Re: Does this sound right about a coil and resistance?

No. Ohm's law will prove it. Without current, there is no voltage drop.

Compare it to a garden hose with the tap just barely on, assume city pressure of 50 psi. If the nozzle is not opened, the pressure at the nozzle will be 50 psi within a few seconds. If you kink the hose (but not completely sealed) the nozzle pressure will still be at 50. Thats comparable to 2 resisters in a circuit.

Until you open the nozzle, and have flow (current) Now there will be a drop in pressure. (voltage)

A good Fluke VOM has 11 Megohms input resistance, so the load presented is negligible.

EDIT

It occured to me, some people are not familiar with Ohm's law. Briefly;
It states that E = I/R. where E is voltage (Electromotive force), I is current, and R is resistance.
If you measure across a resistor in a circuit with no current, and say, a 1,000 Ω resistor, it becomes E = 0/1000. Zero divided by 1000 is still zero, and E is also zero (the voltage across the resistor). There can be 12 volts, or 100 volts dc on the circuit, it makes no difference.

yup, i stand corrected. you'll still be able to measure battery voltage without current flow though.

 

[wire2]

Re: Does this sound right about a coil and resistance?

...
2) is a question , with the points do you have a condenser in the distributor?? I would say you should have . Condensers burn points No, condensers absorb much of the arc of the points opening under a 12 v load. Without one, points would last only a few hours., ballast restricts voltage, no, they restrict current, and that places a voltage in series with the coilcoils magnify the voltage provided from the ballast to the condenser to the points and when the points open u get spark.A coil is a step-up transformer. When the points close current in the primary windings (12 volt side) builds up a strong magnetic field in the coil. The same magnetic fiels also cuts through a few thousand turns of smaller secondary winding, inducing a voltage, but relaviely slowly. When the points open, the magnetic field collapses, inducing a high voltage in the secondary windings, to jump the spark plug gap
3) In the past on autos I found that coils burn out typically when there is a short coming off the (-) side of the coil
4) Wish I knew more about boats as I've never replaced the hoses to a merc outdrives trim, the down hose
Good sailing.!

Ok, I'm done, an Going to the cottage right now for some R&R, including boating.

 

[nola mike]

Re: Does this sound right about a coil and resistance?

yep, 12 would be a problem.

what about 11V? problem??

10V? will that overheat the coil?

9 maybe?

7.3?

he was on the right track. Someone actually using specs from the OEM manual for a change.
Why confuse things?
OMC gave no spec for correct voltage, so he's measuring the resistance.

that's fantastic. the point was that even if the wire checks out, you could still have full battery voltage at the coil from another source. as wire2 pointed out, i guess this is only valid with the points closed.

 

[wire2]

Re: Does this sound right about a coil and resistance?

yup, i stand corrected. you'll still be able to measure battery voltage without current flow though.

yes. voltage will be present in all parts of a curcuit, resistors or not.

 

[Vincentgould]

Re: Does this sound right about a coil and resistance?

Anyone know thecorrect resister for me. 1992 OMC 5.0 ford with electronic ignition and exterior resister coil.

 

[Aloysius]

Re: Does this sound right about a coil and resistance?

You can always go with an INTERNALLY resisted coil. automotive applications allowed the engine to start with no resistor in the circuit, to assure adequate voltage to the coil. Once on the run circuit, they ran through the ballast resistor, to reduce current through the points and minimize burning.