Which Coil With Petronix

[JasonR]

I need to buy a cheapo coil till my marine grade one comes in. I went to the auto part store and requested a "greater than 1.5 ohm resistance" ford coil. I have a 351w with converted points to Pertronix. He handed me several "no resistor needed" coils ment for point style engines. Using my handy dandy ohm meter I found NONE of them to have any resistence from neg to pos. posts. He said that I needed to measure the resistence from either post to the center tower. This is not what the Pertronix describes. I also noted that my original coil did not have any resistence. I'm feeling like I might be doing something wrong. thanks

 

[HT32BSX115]

Re: Which Coil With Petronix

It might be a problem with the multi meter you're using.

The primary winding resistance is measured from the + to the - posts.

The secondary winding would be measured from the NEG and the high voltage output side. I measured about 1.8 OHM on the primary of a coil I have in the garage that states on the side that it must be used with an external resistor. I have used it without a resistor and it got pretty warm.
(14v/1.8ohm equals around 8A ....and 8A x 14v= 112 watts) It's going to get a little warm!


Anyway I used a FLUKE 189 multimeter. Some multimeters do not measure very low resistances very well so it might be the meter that's giving you an inaccurate reading.

If you try to measure the high voltage winding It's possible that you wouldn't measure any resistance at all or a very high reading (very high resistances appear like an open circuit. )



The Pertronix unit can be used with an external resistor or not. I have one on my old Ford truck. I tried it both ways and it didn't make any difference. It's mainly a limitation of the coil.


If you want to verify the resistance in the coil, just connect a 12v battery across the plus and minus posts. put an ammeter in series and measure the current. Take the measured current and divide it INTO 12.

12/AMPS=OHMs ........... You should get around 7 to 9 amps if you have a 1.5ohm coil


Regards,

Rick

 

[pra100]

Re: Which Coil With Petronix

I need to buy a cheapo coil till my marine grade one comes in. I went to the auto part store and requested a "greater than 1.5 ohm resistance" ford coil. I have a 351w with converted points to Pertronix. He handed me several "no resistor needed" coils ment for point style engines. Using my handy dandy ohm meter I found NONE of them to have any resistence from neg to pos. posts. He said that I needed to measure the resistence from either post to the center tower. This is not what the Pertronix describes. I also noted that my original coil did not have any resistence. I'm feeling like I might be doing something wrong. thanks

I just did a conversion on my boat.Long story but it had no dist.,it had a ecm,which died.I put a points type dist. in it,then put a Pertronix Ignitor II.(That is their new one).
Anyway I put a Accel Super coil in,that is that great big yellow one.It came with a resistor that could be used or not used.I hooked it all up,went through the resistor and all is fine.

 

[freddyray21]

Re: Which Coil With Petronix

I used on with a resistor on my Petronix also. works well. Your original wiring on that probably has a resistor wire inline and will provide resistance. Petronix says for an 8cl you should not draw more than 8 amps to the coil.

the following from their website.

What type of coil can I use with the Ignitor™? How do I check my coils resistance? (12V negative ground only)

To determine if your systems coil is compatible with the Ignitor, some measurements should be taken prior to installation of the Ignitor. Caution… While performing this test, never leave the ignition switch on for more than 30 seconds at a time.
Set your voltmeter to a 15 or 20-volt scale. Attach an 18 or 20 AWG jumper wire from the negative coil terminal to an engine ground. Attach positive (red) lead of your voltmeter to the positive side of the coil, and the negative (black) lead to an engine ground. Turn the ignition switch to the run position. Now read the voltage at the positive coil terminal. Turn the ignition switch off. If the voltage measured is approximately 12 volts, no resistance wire is present. A typical resistance wire will provide 9 - 6 volts.
The next step is to determine the resistance in the primary ignition. Label the wires attached to the coil terminals and note their appropriate location. Make sure that the ignition switch is off and disconnect all wires from the coil. Adjust your meter to the lowest ? ohm scale. If you are using an analog style meter make sure to zero the needle. Measure from the negative terminal to the positive terminal. Write your measurement down.
Now the maximum system amperage can be determined, divide your voltage measurement by your coil resistance measurement. This will give you the system current or amperage.
Four cylinder engines should not exceed 4 amps. Six and eight cylinder engines should not exceed 8.5 amps. If the total amperage in your system is higher than the amount recommended for your application, you should install a ballast resistor.
Example Voltage 12
Resistance 1.5
12 / 1.5 = 8
Total amperage 8

 

[JasonR]

Re: Which Coil With Petronix

I have been checking it with the Ohm setting across both smal posts with no other leads on it. They all come up 0. Do I need to have current running through it to get the resistence reading? Sorry for the double post I guess I didn't sign in.

 

[HT32BSX115]

Re: Which Coil With Petronix

Your meter probably won't read LOW resistance values. So it indicates a short (or zero).

If you want to know the resistance connect a battery to the posts thru an AMMETER that reads at least 10 Amps full scale. Most multimeters will do this. read the current (it will be somewhere around 7- 10 amps).


12v divided by 8 amps = 1.5 ohms etc.



The AMP meter, "A", goes in series as shown.

Rick

 

[JasonR]

Re: Which Coil With Petronix

cool thanks Rick and everyone else. I'll try it in the morning.