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thehackmechanic

Has anyone ordered and received a new 2 ohm black coil?

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You'd think this was beaten to death.

You'd be wrong.

Has anyone ACTUALLY ORDERED AND RECEIVED a new 2 ohm black coil that is meant to be used with the original 1 ohm ballast resistor?

This started because, when I bought my tii, it had a Bosch red coil and the original ballast resistor. I installed a Pertronix and it fried it. I put a new set of points and condenser in. It fried the condenser. I found an old Bosch black coil I had lying around, put in another set of points and condenser and it sprang back to life.

I'm an engineer and I like to understand things. I believe the following to be true:

--Total resistance of the primary windings of the coil (across the + and - terminals) plus the ballast resistor should be about 3 ohms; if it's less, too much current gets drawn and cooks ignition components. The Pertronix documentation explicitly calls for "a points-style coil with a minimum of 3.0 ohms of resistance."

--Black coil has 2 ohm resistance, goes with original 1 ohm ballast resistor. I measured all three of my black coils and all three of my original ceramic resistors. (Although this thread http://www.bmw2002faq.com/component/option,com_forum/Itemid,0/page,viewtopic/p,906044/highlight,/sid,ee1356f5bae96c33318cfd5849975676/ shows a Black coil with a label that explicitly calls for a 1.8 ohm resistor. None of the labels on my black coils are readable anymore.) If I'm wrong about this 2 ohm thing, please tell me.

--Red coil has 1.5 ohm resistance, goes with red 1.8 ohm ballast resistor.

--New Blue coil (what you get if you order 12 13 1 359 637) has about 3.6 ohm resistance, has internal resistor, don't use external resistor.

If any of that is wrong, please chime in, but all of the above resistance measurements were performed directly by me on actual parts.

The original Bosch Black coil for a '72 tii is listed in RealOEM as part number 12 13 1 357 240 superseded to 12 13 1 359 637. If you look that second part number up on line, you see pictures of a Bosch Blue coil.

There were references on this site to Blunt (Steve Peterson) having Bosch Black coils in stock. Those references are:

http://www.bmw2002faq.com/component/option,com_forum/Itemid,0/page,viewtopic/t,347639/start,0/postdays,0/postorder,asc/highlight,/sid,4959b92046d2b5570dc26457d6530e29/

http://www.bmw2002faq.com/component/option,com_forum/Itemid,0/page,viewtopic/t,371876/highlight,/sid,742f04895cc00d80262602eab78fcd72/

I ordered one so I could have a brand new ignition system, stem-to-stern, with the original and correct resistance. What arrived has part number 9 220 081 083 on the box and stamped on the bottom. It is blue. I don't care about the color, but it has a resistance of 3.6 ohms. That means it's meant to be used without the external ballast resistor.

I just swapped e-mail with Steve, and he says he got the information that this is the correct replacement for a Black coil from Bill Williams.

c.d. says:

"t.h.m - if it were my 1972 2002tii,

I would order a new resistor 12.13.1.353.362 ($42.62),

and a new coil 12.13.1.359.637 ($53.20)"

On any web site that shows a picture, the part number 12.13.1.359.637 shows up as a Bosch Blue coil that looks just like the one Blunt sent me. I'd wager it has the same 3.6 ohm resistance, and, again, is meant to be used without the external ballast resistor.

So.

Has anyone ACTUALLY ORDERED AND RECEIVED a new 2 ohm black coil that is meant to be used with the original 1 ohm ballast resistor? Or are in fact the only choices for new purchases a Red coil and 1.8 ohm resistor, or a Blue coil and disconnecting the resistor?

--Rob

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Edit... just read that you have the wrong coil. Maybe try to find a good used one?

Get your distributor recurved too. Everyone spends money on the ignition without looking at the worn out springs or wobbly distributor shaft.

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Many years ago I replaced the OEM black coil on my '73 with a blue coil--and didn't bother to disconnect the resistor, mainly because I didn't know that I needed to. I had a Delta Mk 10B CD system on the car at the time, and changing coils didn't make a difference in anything.

I'm still running the blue coil with external ballast resistor, but now minus the CD unit (my old one died, and can't find anyone to troubleshoot/repair it) and everything is working just fine....go figure

cheers

mike

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Justin, the car has a newly-rebuilt distributor, from Jeff at AdvancedDistributors.

Not sure what you mean by "Edit... just read that you have the wrong coil."

I wanted to buy a new black coil for the same reason I had the dizzy rebuilt -- to start with a known good unit. (Actually that's not quite true; I knew the distributor wasn't advancing.)

Is there anything I said you know to be factually incorrect?

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Rob,

I don't think the black coil has been available for years. The new one is red or silver with red label and as you stated needs a 1.8 ohm resistor. I use the red with 1.8, works great. The red with the original 1.0 caused the coil to overheat after 20, 30 or 40 miles, never any rhyme or reason. I thought it was a short in the tach wire but it was really the resistor.

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As of 2 weeks ago the Red Coil is no longer available either FYI.

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From the Bosch Automotive tradition site...

http://www.automotive-tradition.de

Obviously someone at BMW Classic or Bosch want to confuse us... If it were my Tii and I planned on driving it regularly I'd use the Bosch red coil and correct 1.8Ω resistor. That's what I/we sell to most of our '02 customers. The blue coil is known to have less spark strength than the original black with the original resistor.

If I were restoring a Tii to original I'd track down the correct ignition components according to this original Bosch service information.

MF0299.pdf

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I have a 68 2002 with a bosch stickered blue coil and no resistor along with a 008 mechanical advance distributor, standard ignition. For very early cars that had no resistor and probably a black coil, how can you tell them apart from later black coils?

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Here's what I have in my old notes from my days as parts monkey.

Remember! Bosch uses two numbering systems for it's pat numbers.

a) 10 digit "long" number

B) 5 digit "short" number

Coil Nrs (short):

00010 = black coil

00012 = blue coil

00013 = red coil

some or all of these coils will now be silver with stickers differentiating the resistance required.

I'd be really surprised if the red coils (or any of the above) were NLA..though they do LOOK different from the red bodied coils of yesteryear (and by yesteryear - I mean 6 years ago)

If anyone here has used and/or received these numbers and gotten incorrect parts, I'd like to know!

I encountered a red coil on a customer's car recently that had been spraypainted BLACK by a previous owner....the source of some diagnostic head scratching as you can imagine!

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Just for morning banter, Euro cars used a black coil, no ballast resistor and no starter relay. At least the tourings did not. When I got the 72 touring it did not have a ballast resistor nor a starter relay. I checked the wiring schematic and they are not on there either.

So, Paul, if you ever work on my touring, it is a blue coil sprayed black with no starter relay.

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Here's what I have in my old notes from my days as parts monkey.

Remember! Bosch uses two numbering systems for it's pat numbers.

a) 10 digit "long" number

B) 5 digit "short" number

Coil Nrs (short):

00010 = black coil

00012 = blue coil

00013 = red coil

some or all of these coils will now be silver with stickers differentiating the resistance required.

I'd be really surprised if the red coils (or any of the above) were NLA..though they do LOOK different from the red bodied coils of yesteryear (and by yesteryear - I mean 6 years ago)

If anyone here has used and/or received these numbers and gotten incorrect parts, I'd like to know!

I encountered a red coil on a customer's car recently that had been spraypainted BLACK by a previous owner....the source of some diagnostic head scratching as you can imagine!

The 00013 or 0 221 119 030 red coil is silver with red stickers...

00116 or 9 220 081 079 is the NLA real red painted one.... We were able to get a few of these from IMC even earlier this year, but no longer. :(

The 1.8Ω resistor is 0 227 901 014...

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Just to make things more confusing, both of my tiis ('73 & '74) originally came with this type of coil. It's black, but is marked as needing a 1.8Ω resistor, so it's equivalent to the red. It hasn't ever been spray painted to change the color as far as I can tell.

BoschSuper-CoilBlackKW12V.jpg

I swapped it out for a red one because I think they look cooler. I've seen several variations of the old red ones. Some have black tops like the one pictured and some have tan tops like the black one above. Later ones were made in Brazil instead of Germany.

BoschSuper-CoilRedKW12V.jpg

Original 1.8Ω resistor from my '73 tii on the right, new replacement on the left:

Bosch0227901014.jpg

I had to add the tabs onto the new replacement resistor so that I could use the stock push on connections.

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'74 US Tii's have an inline resistor in the wire harness from the #12 fuse. I recall that I've measured that resistor at 1.7Ω, and thus have installed Red coils with no issues.

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'74 US Tii's have an inline resistor in the wire harness from the #12 fuse. I recall that I've measured that resistor at 1.7Ω, and thus have installed Red coils with no issues.

10-4 Tom. I figured that out after measuring the resistance of the wire on my '74 when I borrowed a freinds really expensive Fluke meter for measuring small resistance values. My resistance wire tested out to be 1.8Ω - 1.9Ω. Then I found a reference in the '74 specific wiring diagram in the old Chilton's 2002 manual that says the wire has 1.8Ω resistance on the '74 tii. I ended up running an extra wire for the + side of the Pertronix from fuse #12 so that the Pertronix would be hooked up before the resistance wire and thus get the full 12+ volts that it needs to trigger properly. Both of my tiis are running the red coils with Pertronix.

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