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6 Volt or 12 Volt Coil

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N

Naomi

Jedi Hopeful
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Easy question. My 79 is down again and the hubby was looking in the Haynes 1962-1980 MGB Manual and it says, in the Ignition Section, that earlier cars use a 12 Volt Coil and Later Cars a 6 Volt. In what year did earlier cars end and does the 79 really have to have a 6 Volt Coil? It does and the hubby wonders if that may be the root of the problems we have been encountering with the ignition.


Your turn,
 
12 volt all Sprite and MG from a bout 1958?????????

and I do not know that for a fact but would be willing to bet a beer on it.
 
Tony does that mean it's suppose to have a 6 volt coil on it? The hubby seems to think that it should be a 12 Volt since it has the resistor wire and maybe that is why it is getting a weak arc. The previous owner never really had a great deal of seat time in it and maybe now that it is being driven that is the root cause of the breakdown.
What do ya folks think /ubbthreads/images/graemlins/smile.gif
 
Na - here're the specs on your coil - &, yes, its a 6 volt...Now, I can't tell you what they mean but here they are:
Make/Type............Lucas/16C6
Resistance: Primary.......1.43 to 1.58 ohms @ 68-degrees-F
Consumption @ 2,000 RPM...........1 amp
Ballast Resistor.............1.3 to 1.4 ohms

But, didn't you change your ignition?
 
Yep but it's down again. Sure was hoping Bill was right and a to low voltage coil was burning things up. Now back to square one--oh well he's retired anyway and this will keep him busy /ubbthreads/images/graemlins/smile.gif

By the way those specs are exactly what the coil reads /ubbthreads/images/graemlins/smile.gif
 
Have Bill check the specs on the ignition you installed to see if they match.
 
Woops, I owe someone a beer.
 
Tony they do match. The hubby has also been exchangine emails with one of our friend and he swears that all MGBs use a 12 volt coil. Matter of fact he became a little mad when the hubby used the same reference as I did in one of the above post and the conversation got a little heated. We've looked at numerous sites and they all say 6V for later years. Sure hate he got mad.

Anyway back to square one--weak spark, got gas, good battery, the car won't start. Should I part it out now /ubbthreads/images/graemlins/wink.gif
 
I'll come tow it away for you - don't want you to get in trouble for "yard art" violation....hehehehe

Have Bill try a Lucas Sport Coil
 
I have a suggestion on terminology that my make your friend feel less annoyed. Don't ask about 6V coils, ask about ballasted and non-ballasted ignitions. It's the same thing, just different terminology.

If your car has a ballasted ignition, its coil will have a primary resistance around 1.5 Ohms as stated above. (Disconnect the coil low tension wires from the coil to measure this... don't measure it with the wires on). The wiring to these coils will include either an external ballast resistor or a resistor wire (pink? in color) from the ignition switch. There will also be a wire between the coil (+) terminal and the starter solenoid. These coils are sometimes referred to as 6V coils. It obviously doesn't mean the car runs on 6V.

I don't know when BL started using ballasted ignitions but I don't doubt a '79 might have one.

EDIT: Sorry, I meant to add that if you want to determine what type of coil you NEED, perform this additional test. Make sure all the "normal" wires for your car are connected to the coil. Connect a volt-meter between coil (+) and chassis ground. Now connect a jumper wire between coil (-) and chassis ground. Turn on the volt meter, then turn on your ignition. If the reading is 6 to 9V you need a ballasted coil because somewhere there is a ballast resistor/wire. If you measure 12V, you need a standard coil. You need the jumper wire in the circuit to make this measurement so you'll know current is flowing through the coil. If current isn't flowing (points open) you'll always read 12V... regardless of whether there's a ballast resistor or not.
 
And what voltage shall that Lucas Sports Coil be /ubbthreads/images/graemlins/smile.gif

PS: Tony ya ain't getting the 79!!!
 
The 'ballasted' Sports coil will be correct for your car - just more 'umphf'.

Doug - good explanation - I learned something also!
 
The hubby spend about 4 hours on the darn thing today and has now declare himself as "defeated"! He did figured out the electronic igition works somewhat like a camera shutter. There is a disk placed on the shaft with four slots in it, one for each cylinder. The pickup is a light light and a sensor with the disk rotating in between it. When an opening in the disk allows the sensor to see see the light it allows voltage to the coil just as a set of points would. It can be adjusted and he does have it on the mark. As a matter of fact he took the timing light, connected to #1 spark wire, turned the ignition on, held the trigger on the light, and he and I pushed the the car in forth gear until the timing light came on. The timing mark was a 10 degrees before top dead center. He then removed the distributor cap and the rotor button was pointing exactly to where the #1 plug lead is located. With the cap off he placed the coil wire near chassic ground and would get an arc about 1/4" (yellow) as he turned the disk (shutter). Very similar arc with the plug wires. Put it all back together and it didn't even try to fire. He then sprayed some starting fluid in the carb and still the same, just as if it was not getting fire at all.
He says he knows he is overlooking something but just can't figure it out. He is most open for opinions and suggestions and says he also has this thought in the back of his mind that there is another problem associated in additon to the ignition. By the way he did trace all the wiring to insure it is correct and it is. One surprise to to him is that all later model MGBs acutally use 6 volt coils or should used them. He was thinking that was a misprint in my Haynes Manual until he went online and numerous companies do advertise the 6v for late MGBs and 12v for early MGBs. Both my 79 and 80 ohm out as 6 volts on the secondary windings.
Now how did I know all of this---I copied one of his emails to a friend and paraphased what he had written. Needless to say the 79 (Bandit) is still broken /ubbthreads/images/graemlins/frown.gif
 
Hang in there.
The yellow spark doesn't sound good, but 1/4" jump certainly should be enough.
 
6 volt because of the balast resister.... It cut the voltage in half... so the points don't get fried. That's why it's a 6 volt coil. Have you changed the ignition system to a new one yet? You were having this same problem about a month ago (same car no?). I still say it's the little black box, (and maybe the light sensor included in that setup).

Do you have a new one in, and it's just not working? Or is it still the same one? If the same one, it's broken, and not to be fixed... get another one and install it to instructions. If it's a new one, then I'm out - no new info to add.
 
Doug that's what he says and can't understand why it isn't trying to hit. The engine just turns over and over and doesn't even try to start. By the way it is getting fuel:smile:

Help, Help /ubbthreads/images/graemlins/frown.gif
 
Kenny it is an new Crane X-700 (identical to the other one). Please don't be "out". Do you think there is another problem other than the distributor? Hey the hubby is about to give up on ole Bandit /ubbthreads/images/graemlins/frown.gif
 
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