Bosch Blue Coil question

jlond70 · Post by **jlond70** » Mon Sep 03, 2007 10:05 pm

I have a nos Bosch Blue Coil (12V) from quite a number of years ago - made in Germany. Were these older Bosch Blues internally ballasted like the newer ones?
I have a 70 Spider and I still run with the original single points set up, with one of the new Bosch Blue coils that don't need the external ballast resistor. I have heard and read that the older coils are better. Would I have to add the resistor if I use the older coil?

Josh

So Cal Mark · Post by **So Cal Mark** » Mon Sep 03, 2007 10:39 pm

I seem to remember the early cars having a ballast resistor mounted on the fenderwell next to the coil. Is yours still intact?

jlond70 · Post by **jlond70** » Tue Sep 04, 2007 9:33 pm

I looked for the ballast resistor in the fenderwell near the coil - nothing there.
Can I test the old Bosch coil and find out if I would need the ballast resistor if I use that coil?
Thanks,
Josh

mdrburchette · Post by **mdrburchette** » Wed Sep 05, 2007 6:07 am

I don't recall having one on any of mine either.

manoa matt · Post by **manoa matt** » Wed Sep 05, 2007 11:06 pm

The Bosch blue coil should be internally ballasted. It is a newer style coil that has the internal windings surrounded by a solid epoxy.

The older style coils are filled with oil to help them stay cool.

Newer epoxy coils have better vibration resistance, (good for off road)
Older oil filled coild have better internal flashover protection.

If your car is running good with the blue coil, then just go with it.

I have a 78 that I converted to single points. My origional oil filled coil was flashing over at the tower and causing a misfire. I bought a bosch blue coil and could not even get a spark. I then bought a coil with the same specifications as the OEM coil. It worked for a while, but the coil would overheat after 10 min of driving and short out for a couple hours. I tried several ballast resistors and could not get the coil to stay cool.

I'll post a link later when I get home regarding: calculating the ballast resistor needed for a coil. But like I said before, if its running good with the blue coil, there is no need to buy extra parts.

Matt

manoa matt · Post by **manoa matt** » Thu Sep 06, 2007 8:46 pm

Here are the links, be careful how much advise you take from the articles, as some of them are ment for VW's .

This article discusses how to size a ballast resistor to a coil:
http://www.hot-spark.com/Coil.htm

Even though your set up does not include an ignition module, I can't imagine any 12v coil would perform well with more than 4 amps and more than 12volts.

This article dicusses the good, bad, and ugly Bosch "blue" coils, apparently some are junk.
http://www.ratwell.com/technical/BlueCoil.html

This article discusses improvements to a stock coil, and the operations of a mechanical ignition system vs electronic:
http://www.vintagesaab.com/sonett/ss/Hi ... PoCoil.htm

Hope these help.

Matt

jlond70 · Post by **jlond70** » Thu Sep 06, 2007 10:50 pm

Thanks Matt, these are great articles. The car is running fine with the newer Bosch Blue (internally ballasted)- made in Brazil. I'll do the ohm tests listed in the article on that one and on the nos Blue I am not using - it is an older one from when they were made in Germany. If they come close then I would think there is also the ballast resistor built into the old one.
Unrelated to Bosch coils, and surely more interesting, it must be great driving a Spider out there in Hawaii.
Do you know Stan Rhoden from Kaneohe?

Josh

manoa matt · Post by **manoa matt** » Thu Sep 06, 2007 11:34 pm

Just be carefull what you decide to do. I don't want you to fry your coils.

I don't know Stan, is he the one with the red spider? I think his handle is "Hawaiian spider" Theres only a few fiats on Oahu, and I try to leave a business card on fiats that I see.

It is fun driving a spider here, except for the potholes, Hawaii's roads are 5th worse in the nation, my alignment about 100 miles ago is already out of wack. Also everyone is layed back and drives like a grandmother. People actually drive 55 on the highway, and they inforce it!

There are so many micro climates you have to be carefull and watch the skys. It might be clear and sunny, but 100 yards down the road it could be pouring. I live in the back of a valley at the base of a mountain range. I get about 200 inches of rain per year at my house. One mile down the road towards the ocean they get 90 inches.

It is intestering to note that with all the salt air there are alot of crusty rusted out cars everywhere, but there is also a dispoportionatly large number of classic cars, in good shape. Tons of old beetles and VW buses. I think If I wasn't renting and had some space I'd have another Fiat, an International Scout, and a few Alfa spiders by now.

With so many cheep classics available, I'd love to buy a few, fix them up and start a classic car rental bussiness. Imagine vacationing in Hawaii and driving around for a week in a Fiat spider, or an Alfa, or a suped up VW.... To much liability, and not enough reliability.

So Cal Mark · Post by **So Cal Mark** » Fri Sep 07, 2007 1:32 am

one important thing to check with points is how much voltage you have at the points. The ballast resistors were used to cut voltage at the points; too much will result in arcing that will burn the points quickly. With the key on, points open, check the voltage at the points. If you have battery voltage, plan on installing a resistor or expect to change points monthly