Ignition coil wire color question???

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qcabra

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First of all, thanks to everybody for creating this wonderful forum.

I just bought a 1974 3.0CS coupe that needs a lot of work.

Does anybody know where there is a good photo of an ignition coil that shows which wires go where or can anybody say where each wire goes? Specifically, on the coil, it is marked positive on one side and negative on the other. I know the coil wire goes in the middle but it looks like 2 wires go on the positive side and 2 on the negative side. The question is, which ones go where. I downloaded a wiring diagram but It's not clear to me which ones go where. I searched on the forum and haven't found it. Gonna buy the book for the car this week. Thanks in advance.

Once again, thanks for such a great forum. I hope to contribute some day.
 
Generally on a coil the "+" positive terminal connects to the ballast resistor (or +12 ignition if no ballast) and the "-" negative terminal goes to the points or electronic ignition. Also, the tach and speed sensors go to the negative terminal.

The coil will probably have 2 or three spade connectors on each side. The ballast resistor will be a ceramic box (about 0.5"x0.5"x2") with two leads (+12 in from ignition relay and +12 out - not directional). There may also be a capacitor (small black box - 0.75"x0.75"x0.5") with a single wire that will go to the positive coil terminal. This capacitor, if present, is NOT the condensor for the points. The negative terminal wire to the points connects into the side of the distributor near the screw where the condensor is mounted. On my coupe the tach wires are a pair of black wires in a separate connector; they route down to some silver boxes with black labels (if original) below the coil.

This may be the other way around in OZ, I know their toilets spin the other way and they may run positron (hole) based circuits there rather than electron based. :wink:

I hope this helps.
 
Hello again, thanks for the prompt replies. I'm not getting any spark from the plugs so I'm working my way back from the plugs toward the battery.

Bought a new coil. The ignition is missing so it's just a bunch of wires under the dash so I'm hoping it's something stupid like a relay or the brake pedal has to be depressed. Got the volt meter out today and I'm on the hunt.

Thanks again for going out of your way to help. Take care.
 
This has nothing to do with the brake pedal, it is only the ignition switch.

1. Check for +12 volts on the + side of the coil. If it is not there then you can jump directly to the battery for a quick test.

2. Put the meter on the coil negative side and crank the engine (use a high voltage setting if it is not auto-ranging. You should see the voltage go from 0 to 12 to 0 to 12 as the engine turns and the point close.

3. Inspect the cap and rotor.

4. Measure the resistance of the coil wire and each of the spark plug wires. They should be less than 200 ohms and almost 0 ohms if they are solid core.

5. With the + and - connections removed from the coil measure the resistance across + and -. I am not sure of the precise value but I would think probably <20 ohms. If the coil is burned out the resistance will be very high. You can probably buy a cheap coil at a local part store as a quick test too.

I am sure someone here can give more precise resistance values - mine are just off the cuff but close enough for basic testing.
 
hmm

is it just me or does anyone else share the feeling that a first time coupe buyer, who gets a unit that "needs a lot of work" and can't read a wiring diagam, could be in for a lotta trouble?

Well we're here to help, and good thing too. Sorting the ignition should not be a major challenge. Replacing a coil though seems to be flailing. You reported no testing of the coil to see whether it was any good. They seldom go bad...

Understanding the system you have to work on will go a LONG way toward saving you time and money, and that understanding will help you later if the system craps again. Which, given the Mechanic's Rule that the first place to look for trouble is the last thing you touched....
 
Hi,
Thanks for taking your time. I've tested the things you listed and things have checked out so far. I really appreciate the input. I'll figure the rest out. I don't want to take too much of your time but thanks for helping me get a head start. It's been very helpful. My original question was geared toward making sure there weren't wires that were physically missing. Some of the pieces weren't there from the beginning.

As far as being in over my head goes, you're right I am. However crazy, it's part of the plan. I partly bought the car because I wanted to learn more about engines, welding, and body work(not Bondo). What better way ,besides going to school or apprenticing somewhere, than to buy a great car which needs a decent amount of work that at the end of the day is worth the trouble.

On another note, you're right too about it being a good thing that you guys are here. Thanks again for the help. The forum, Google , and Youtube are my friends . It's great to find info here.

This is nothing compared to many of the other things I've done. When I wanted to learn more about diesels, I bought an older Mercedes diesel and fixed that up a bunch. To me, it's a pleasure to diagnose while learning.

My biggest concern is that I might have to go away for work and not be able to return to the car for a while but it doesn't matter too much relative to what I'm learning.

Once again, thanks a lot for all the input. I'm enjoying the journey while on the journey! It's been a lot of fun.
 
Status update:
I got it started!! The PO removed the ignition coil among other things and the wires were all over the place. It was a matter of unplugging and testing a bunch of wires along with the Bavaria wiring diagram that is linked from this site. I cleaned the connections and hooked up the right wires in the right place and it started. Thanks for all your help.
 
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