• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Getting spark

Share this page

S

sp8

Freshman Member
Offline
Hi! I'm new to this but I have recently purchased a 65 AH 3000. It's a beautiful car but it has sat for 10 years (garaged and covered). I have done all the usual sort of things to get it running but now I'm struggling to get spark. Somewhere along the line, someone converted my car from a positive ground to a negative ground. I have recently replaced the coil. The old coil had the SW and CB designations and my new coil has the + - designations. The old coil only had two wires on it. One wire went to the switch and the other wire went to the distributor and that was it. Looking at the schematic in a service manual (albeit a positive ground schematic) there looks like there should be three wires. Besides the two I already have there looks like there is supposed to be a wire connection back to the battery switch. Sure enough I found a W/B wire in a wire loom but it was cut off and taped (W/B wire is supposed to run back to the battery switch). Is this wire supposed to be connected to the - side of the coil? or is there a reason that this wire would be cut? Is there a posting somewhere that shows the schematic with a negative ground?

Thanks in advance for any help!
 
Hi SP8,
Welcome to the forum and congratulations! SW stands for switch (ignition switch) so on your car, the switch would be +. CB stands for contact breaker (points), that gets the -. You are correct about the white/ black wire connecting the coil to the battery switch in the trunk. A fair amount of people have disconnected that wire when the switch goes bad.
 
The wire going back to the battery switch is a security feature, and is earthed when the switch is opened to suposidely prevent hot wiring to start the car from under the bonnet. Notorious source of problems which is why it is probably cut off.

Wire a 12v bulb across the coil + and - terminals, and satisfy yourself that it goes on and off as the contact breaker opens and closes. If it doesn't then you need the find out why !

AWEM
 
How is the complete circuit made up with that wire removed from the circuit? Or does the switch act to ground the coil when the battery is disconnected so that you can't start it from the engine compartment? Obviously the schematic in the service manual is pretty non-descript on how the switch works. Thanks for the info.
 
[ QUOTE ]
Or does the switch act to ground the coil when the battery is disconnected so that you can't start it from the engine compartment?

[/ QUOTE ]
Yes ----
D
 
I would have never suspected that looking at the schematic. Thanks for the feedback, that makes me a lot more comfortable with the troubleshooting.
 
Yeah - A lot of folks have trouble with the wire getting grounded when it shouldn't be & disconnect this wire. If the battery switch gets worn or screwed up, it can ground the wire while the battery is turned on. I guess whether you like this feature or don't, depends on if you intend to leave the car unattended on the street over night. A knowledgeable person can still hot wire the car in less than a minute. Just clip the grounding wire at the coil & plug the upper fuse into the block slightly below it's intended position.
D
 
Back
Top