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Coil voltage question
https://www.slantsix.org/forum/viewtopic.php?t=19036		 Page 1 of 1
Author:  Eric W [ Sat Aug 05, 2006 9:39 pm ]
Post subject:  Coil voltage question
I tested the + post on the coil today with engine running. It read 7.45 or so volts. So I tested the ballast resister......3.0 ohms. It was so hot it melted the plastic wire loom holder underneath it where it was touchng! I put another BR I had laying around (literally...in the trunk) and tested at .6 ohms (a .5 was stamped on one of the blades). Tested coil + voltage agian and got a reading of just over 9 volts. A good thing? Running a MSD Blaster 2 coil. For grins, I also tested the - side of the coil and got 4.75 volts. :?: Normal?
Author:  SlantSixDan [ Sat Aug 05, 2006 9:57 pm ]
Post subject: 
Sounds like your old ballast resistance was too high, to me...which ignition system are you running, again?
Author:  Eric W [ Sat Aug 05, 2006 10:18 pm ]
Post subject: 
Running the stock Chrysler electronic ignition. I use a single ballast, not the dual type. ECU came from Napa.
Author:  LUCKY13 [ Sun Aug 06, 2006 2:21 am ]
Post subject: 
Hum, maybe I need to go read up alittle because its been awail sense I have done any of the stock ignitions but I didnt think that Electronic Ignition used a BR, just the piont systems. But like I said its been awail & I my be wrong. So dont do anything rash until checking this out( like remove the ballast).
Author:  LUCKY13 [ Sun Aug 06, 2006 2:21 am ]
Post subject: 
Sorry, hit button twiced.

Jess
Author:  Sam Powell [ Sun Aug 06, 2006 5:39 am ]
Post subject: 
If you take out the ballast resister in the electronic ignition it will burn up the ignition box. .9 volts is safe.
Author:  SlantSixDan [ Sun Aug 06, 2006 8:23 am ]
Post subject: 
Quote:
Hum, maybe I need to go read up alittle because its been awail sense I have done any of the stock ignitions but I didnt think that Electronic Ignition used a BR, just the piont systems
No, the Chrysler electronic ignition does use a ballast resistor. Early type used a dual ballast resistor, later types used a single.
Author:  LUCKY13 [ Sun Aug 06, 2006 10:10 am ]
Post subject: 
Cool. Thanks for clearing it up for me. Like I said it had been awail. I have got use to MSD & I dont use a ballast on them.
Author:  RossKinder [ Sun Aug 06, 2006 12:09 pm ]
Post subject: 
Quote:
Quote:
Hum, maybe I need to go read up alittle because its been awail sense I have done any of the stock ignitions but I didnt think that Electronic Ignition used a BR, just the piont systems
No, the Chrysler electronic ignition does use a ballast resistor. Early type used a dual ballast resistor, later types used a single.
What if you have a Mopar distributor but not a Mopar controller?
Author:  Sam Powell [ Sun Aug 06, 2006 6:42 pm ]
Post subject: 
That is a different issue. If you use an MSD box with a Mopar distributor, you do take out the ballast resister. I have put 100K miles on just such a setup in this car.
Author:  Eric W [ Sun Aug 06, 2006 9:35 pm ]
Post subject: 
Meanwhile, back to the original question.......
Author:  Sam Powell [ Mon Aug 07, 2006 6:29 am ]
Post subject: 
That is a good question, and one which has never been answered definitivly to my mind. You hear between 8 and 9 volts is fine. Seems kind of vague to me. It is kind of hit and miss depending on the ballast resister you end up with. The thing is, it is in the system to allow varying voltage to the coil, depending upon the load on the engine. So it changes continually while you drive. This, I think, is to save the coil, and keep it from working hard all the time. Correct me if I am wrong here, but this is what I have been told.
Sam
Author:  KBB_of_TMC [ Mon Aug 07, 2006 10:27 am ]
Post subject: 
I've tested several ballasts and coils.

The point-style ballast usually reads about 0.5 ohm cold and ~2.5 ohms hot - it is designed to heat up and limit the current; at high RPM, the RL charging time of the coil reduces the average current and lowers the effective resistance (just as described in the 1965 factory manual).

The elec-style ballast stays about 1 ohm hot or cold.

It is normal for the ballast to get quite hot. If you used a lower than stock primary resistance coil, the ballast resistor will be hotter than stock. Stock coils have around a 1.5 ohm primary and around 2.4mH inductance.

You can interchange ballasts and coils between the two w/o much concern - they're close enough to work.

The (-) coil side should be either near +12V (points open or transistor off) or near 0V (points closed or transistor on). The (+) will be +12V or ~8V. Running, it'll appear something odd in between; there will be up to -300V short voltage spikes mixed in.

With the engine running, the voltages are jumping around so you'd need a oscilloscope to really look at them; your #s sound very typical to me.

The factory elec. system draws ~50% more current at idle than the factory point system, due to the difference in ballast. That puts more strain on the ignition switch and wiring, and will show up as a voltage drop at the IGN side of the ballast resistor.
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