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Thu Jan 15, 2004 5:56 pm

I am just getting started putting a Pertronix unit in my 72 bus. I have a Blue Bosch coil. Then I read that there is only one out of five blue coils that I can use with the pertronix. Aircooled said that I need to have a 3 OHM ballast resistor in my coil. How do I know which coil to use other than buying one from aircooled.

Thanks
JEFFRO

Thu Jan 15, 2004 6:45 pm

I read that at ACN also. When I asked about the 5 coils at STF I was told that the originals were oil filled and the new ones were epoxy so all you had to do was shake them. Well, I shook an original coil the other night and I didn't hear anything and it's never leaked so I'm still confused.

I know some have no label, some have a silver label, some have no part number of the bottom (I think all of those go in the crappy category but I'm not sure and I'd like to hear the answer). When I thought there were only 3 coils it was my inderstanding that only one had the ballast resistor inside. That's the one ACN sells. The ballast variety supposedly costs more but I don't see how you can use that to determine if a vendor is selling the "best" one.

The Bosch blue coil I have has a 3.4 Ohm primary. I used it with a Pertronix and it works fine. I didn't get it from ACN so I know nothing about it.

Thu Jan 15, 2004 6:50 pm

I've never heard of needing a ballast resistor with a Bosch blue coil, or any other type of stock VW coil. You need a ballast resistor when you use a MSD or high performance coil that is supposed to work with an ignition control box. The pertronix will directly replace your points and condensor....if you didn't need a ballast resistor before, you probably won't need one with the pertronix either.

Thu Jan 15, 2004 10:31 pm

i just installed the epoxy filled msd coil the other night, WITH a ballast , and when i tried to acellerate, it felt like the engine was "hiccuping". i ended up putting the bosch coil back in, roadside , cuz i didnt have the time nor patience in this cold weather, to mess with it, i dont know if it was going THAT lean from the extra spark or what, but i was thoroughly disgusted, and said screw it , and returned it (advantage of working at a parts store) "defective". I was so stoked to have a performance brand coil too, and it just sorta crapped out on me. it ran fine with the stock coil , but i bought one of them pen testers from snap on , and the spark seemed kinda weak (dull orange in the visual indicator) , i actually replaced it 2 weeks ago with a "standard ignition" green box (the cheap line) UC3T ( "T" denotes the green . cheap line) and within 2 weeks, it was leaking already , which i assumed was because it couldnt handle the vibration (thats why i decided on msd's epoxy filled one).

Anyone else have any similar experiences ?

Fri Jan 16, 2004 2:57 am

From the Pertronix web site... http://pertronix.com/tech_support/troubleshooting.htm

Quote: 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

A stock bay never had a built in resistance in the primary ignition wire to the coil, so you should have 12V on the first test. If your coil resistance is then close to 3 ohms you're in spec @ 4 amps. If your coil resistance is less than 3 ohms you should add an external ballast resistor. :wink: