Bosch Blue Coils
by Richard Atwell
(c) Copyright 2004-2011
Bosch Blue Coilsby Richard Atwell |
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Can you buy the "wrong" 12V Bosch Blue coil? Well apparently, you can. I've never seen such variety in a single electrical item. I've collected all the information I know on Bosch Blue coils to help you find the right one. The more of these we buy the longer hopefully it will be produced.
A 72-79 Federal bus came with a black coil 022 905 115C and a common "upgrade" includes switching to the hotter blue coil, sometimes called the Bosch Super coil.
According to Brian Verbeek, the Blue coil is less powerful than the OEM black version but I haven't been able to prove that through measurement. They appear to operate nearly identically.
So what makes one coil different from the other? The ballast resistor. This is a resistor inside the coil on the primary side that reduces the current flow partly so the points don't burn up. You can detect the presence of the resistor by measuring the ohms of primary side of the coil (terminal 15 vs. terminal 1). Because the primary is mostly copper wiring (virtually zero ohms), the presence of a resistor is usually easily detected.
When upgrading to a Pertronix Ignitor many people switch coils to get the most out of it but it won't hurt it you keep the stock black coil unless it's worn out. I've done some mileage tests on long trips and accounting for the terrain (hills and wind conditions) it appears that the blue coil gives slightly better mileage but that could simply be compared to the original 25 year old black coil. I'd like to do some more scientific testing to find out exactly what the true benefit is (the coil is basically a step-up transformer and the blue coil with its altered windings and lower resistance should result in a spark with more energy).
Whether you are running stock points or the Pertronix, you need a coil with the ballast resistor inside like the original black coil and this is the heart of the problem with regard to all the copies out there. Unless you add an external ballast resistor, running the wrong coil could fry your Points or your even more expensive Pertronix.
If you have a CDI setup with a conventional coil keep in mind that you don't need a ballast resistor inside. The modification you require is a rotor with the resistance removed.
I took some measurements from my coils to compare them:
Bosch Black coil (factory original Germany)
0 221 119 020 or 00015 (VW 022 905 115C)
turns: 100-1 (unverified)
primary: 3.0 Ohm
secondary: 9.83 kOhm
Bosch Blue coil (Brazil)
0 221 119 027 or 00012 (VW 043 905 115C)
turns: 150-1 (unverified)
primary: 3.4 Ohm
secondary: 7.79 kOhm
The 1/79 fiche I have lists 5 different coils:
I've also seen the 022 905 115A stock coil in a 72 bus. It's the short black one. I'm not sure what's different about it other than it's shorter.
The French call it Bobine Bleue and use the 043 905 115AC part number.
I haven't been able to verify this but the Bosch number for the blue coil WITHOUT the ballast resistor could be 00012A.
The fiche and the coil I have don't seem to match but that's always the way with seemingly identical parts isn't it?
VW currently only lists coil part number 043 905 115C and doesn't even list the original black coil anymore. That blue coil from the dealer is Made in Mexico and costs $60. I haven't seen the coil up close but my friend at the dealer had the CA warehouse staff pull it from the shelf for an inspection and it appears to be the exact same ballast version you can buy for $30 at your favorite online VW vendor.
NOTE: keep your original bracket: it's fits the Type 4 fan shroud unlike the shiny one in the box which is meant for mounting the coil to the Type 1 shroud.
According to the smart folks at the Shop Talk Forums, only one coil is worth purchasing (the Bosch made in Brazil). It can be identified by 4 tests:
These tests don't seem that conclusive to me but that's all there is to go on. Apparently there are even counterfeit Bosch coils out there!
The Bosch Brazil coil I purchased from Bus Depot seems to pass all of these tests. Here are photos of all the known blue coils out there to help to avoid the wrong choices.
The Good: |
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At one time all the coils came from Germany. This one is a NOS 6V version to show you what they are supposed to look like new (don't you just love that old school hammer finish on the distributor?) The 6V version is Bosch 0 221 101 003 6V measurements: 1 Ohm primary winding, 10 kohm secondary. |
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Here's a Genuine German Bosch 12V coil Some idiot painted it metallic blue but the top I saw had Germany written on it. 0 221 119 027 |
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Made in Spain (next best thing to Germany). Good lucking finding one of these since they haven't been importing these from Spain for almost as long as Germany. They've been available in Europe but my last attempt to get one (7/05) I was told by the vendor that the distributor just ran out and switched to Brazil made coils. |
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Made in Brazil. This is the coil that passes the 4 tests (don't go by label alone) Purchased from Bus Depot about 2 years ago. Just as good as the two above. |
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Another photo of the above coil. Bosch 9 220 081 083 (0 221 119 027). The first number is the part number for this coil. The second is the number of the coil this coil replaces (the German 12V coil, yay!) This yellow box and the two numbers on the bottom seem to be an identifying feature of this true blue coil. |
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It also comes in the older style Bosch packaging. |
The Bad: |
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Unknown blue coil. Could be labeled non-resistor... |
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Made in Mexico (Robert Bosch, SA DE C.V.) with no label. Bought from Bus Depot two years ago as part 00012. Written on the coil itself is "ohne vor Widerstand (without pre-resistor) without resistor". The Box has a non matching photo and has a printed part number 9 224 771 008. This coil is oil filled with primary resistance 3.8 Ohms and secondary 4.92 kOhm (<- way to low) |
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Made in Brazil coil sold in Europe. It has been known to have Lucas ("Prince of Darkness") markings on it under the Bosch label. They really call it the blue coil! If I couldn't pick a coil from the "good" section above, I would use this one. Bosch 0 221 119 027 |
The Ugly: |
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Unknown coil probably from Brazil. California imports offers two blue coils. This is their low cost 0-221-119-027 model. The more expensive coil goes by the Bosch short number 00012. At least you have an idea with that vendor that a cheap coil exists. Look: this one doesn't even come with spaded terminals! No kidding (check the box). If you are persistent you can find the terminals and nuts but not at the local parts store otherwise you'll have to reuse some old ones. |
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Made in Mexico with silver label. Another no terminal dud to avoid. Bosch 9 224 771 008S |
I have very little information about the suitability of either of those last two coils but they appear to be losers.
So there you have it. Remember, the coil is THE source of spark energy and the plug wires are responsible for transmission of the spark. Don't underestimate their importance and stick with what we know works and spend a few extra bucks (Bosch Brazil).
If all of this seems confusing remember there are the non-Bosch coils out there that are even more scary!
01/28/04 - Created
05/27/05 - Minor edits
09/06/11 - Fixed broken photos, added translate button, updated footer
07/15/19 - Google update: new adsense code, removed defunt translate button