Hot wire to ignition coil

M

Michel B

New Member
Hi,

my wire to the coil has always 12 volt no matter if the ignition key is on or off

now I understood that the coil gets its 12 volt from the startermotor so my first thoughts were that something was not connected the right way.

seems out that it is connected correctly. But on the wire that comes of the startermotor I have no volts ignition on or off. So that explains why I have 2 wires running to the + on the coil. (Both white with a yellow stripe) one is hot the other not. And my suspicion is that the wire that has no voltage comes from the starter.

what does this mean?
 
Michel B said:
Hi,

my wire to the coil has always 12 volt no matter if the ignition key is on or off

now I understood that the coil gets its 12 volt from the startermotor so my first thoughts were that something was not connected the right way.

seems out that it is connected correctly. But on the wire that comes of the startermotor I have no volts ignition on or off. So that explains why I have 2 wires running to the + on the coil. (Both white with a yellow stripe) one is hot the other not. And my suspicion is that the wire that has no voltage comes from the starter.

what does this mean?
Click to expand...

it is a 3500 P6
 
One wire should come from the top of the fuse box and is ignition controlled, so only live with the ignition on, and has been through a ballast resistor to drop the voltage.

The other wire comes from the starter motor and is only live when cranking the engine, so gives the coil a full 12V to help it start.
 
I hate to say this Michel, but if you are struggling with these electrics, please ensure that you can disconnect the battery quickly, possible with a quick release system, and make sure you have a fire extinguisher to hand. Also, don't leave the battery connected if you're not with the vehicle.

Spares car
 
quattro said:
I hate to say this Michel, but if you are struggling with these electrics, please ensure that you can disconnect the battery quickly, possible with a quick release system, and make sure you have a fire extinguisher to hand.

Spares car
Click to expand...
Absolutely. Although the car runs. But cannot switch it off because is always has power to the coil. I already lead a switch controlled wire to the coil but that is being cut of when the starter goes round. On the other hand the wire that has no voltage is probably the wire coming from the starter and has only Volts when the engine cranks. Now you got me thinking. I did not check the wire form the starter while cranking the engine. If that wire has power only during cranking the engine then I can use the wire I connected to the fuse box (switch controlled)
 
Has the car been fitted with an electronic ignition in the past? Some need 12v to function, if a previous owner has fitted it and used a permanent 12v feed that could be your issue. Also, the ballast resistor in the loom can fail. If they have replaced the wire without a resistor you can have 12v on all the time. Does the rev counter work still on your car? Both the ballast resistor and tacho are in series from the points to the (-) side of the coil. With a ballasted system you'd normally have that side permantly connected to the coil with a second wire coming from the starter that would produce a full 12 volts during startup. Not sure if the above helps at all.

The (+) feed to the coil is normally 12v if measured against a normal ground point. If measured from the wire coming from the points with a ballast resistor fitted it should read around 9v. As @quattro says, the 12v feed should be dead with the ignition off. That could be caused by a bad ignition switch (are other systems that should turn off when the key is off still live?). Or something misconnected by a previous mechanic or owner (More likely). I think its time to pull out the wiring diagram and the multitester!
 
The wire from the starter does not provide the 12 volt. I need to check if this is also the case on the starter. (Maybe a bad wire). The permanent 12volt feed is a white wire with a yellow stripe. The wire from the starte has the same color coding but is a bit thinner. With the ignition switch switched off the interior lights goes out ( should’nt that be a permanent 12 volt as well ?)
 
Michel B said:
With the ignition switch switched off the interior lights goes out ( should’nt that be a permanent 12 volt as well ?)
Click to expand...
Yep, that’s definitely wrong! Sounds like the ignition switch or some really bad fettling by a PO.
 
I would expect a coil with permanent 12V on it (with a circuit to earth) to get pretty hot! Noticeably so!If I work on my car with ign on I disconnect the coil lead.
 
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