Coil - + and - terminals?

[chriscburgess]

Hi,

How can i tell which is the positive and negative terminals on the coil please?

I am attempting to install a tacho and need to attach the green wire from the tacho to the negative terminal.

My terminals are labelled either 1 or 15 with a green wire currently going to 1 and a number of black wires going to 15.

Many thanks
Chris

[CJH]

Pin 1 is the negative terminal, so your tacho green wire goes to the existing green wire. Pin 15 is an ignition controlled live, so one of those black wires is the supply, and the others will be to things that need power when the ignition switch is on.

There's a handy reference for these pin numbers here.

[chriscburgess]

many thanks. That helps.

So if i put my green wire to the pin 1 on the coil can i then just put the red coil wire direct to the battery + and the black direct to the battery negative and get the tacho working?

[CJH]

I think so. It would make sense that the red wire is only live when the ignition is on, so find an ignition controlled live. Don't forget to include a fuse - either connect to the fused side of an ignition controlled circuit in your fuse box (making sure the total of all circuits on that fuse doesn't exceed the fuse value), or put an inline fuse on the red wire.