Which side of the coil is negative? (1 Viewer)

[yesmar]

I am installing a tach in a 1982 FJ40. I need to tap the negative side of the coil, but there are no markings on the coil and the wires are both same color (all original wiring and coil, I think). The wires all seem to go to the igniter on top. Both post on the coil complete a circuit to ground on the chassis with no power on at the switch. How else might I see which is negative?

 

[pithicus]

With the ignition on, I assume only 1 terminal will read voltage. [8 to 12v] , and that will be positive.

 

[pjohnson]

Most all coils I have seen are marked with + and -

 

[yesmar]

Most all coils I have seen are marked with + and -

No markings except 12v

 

[pithicus]

If the 12v marking is near a terminal. that will be positive. With the ignition on you should only get a voltage reading from one terminal. That will be positive. If you are getting a reading from both terminals you may have to disconnect both wires and test them both with the ignition on. You can use a test light if no multimetre.

 

[yesmar]

With the ignition on, I assume only 1 terminal will read voltage. [8 to 12v] , and that will be positive.

 

[yesmar]

If the 12v marking is near a terminal. that will be positive. With the ignition on you should only get a voltage reading from one terminal. That will be positive. If you are getting a reading from both terminals you may have to disconnect both wires and test them both with the ignition on. You can use a test light if no multimetre.

You are correct! Thanks... I did have to disconnect the wires...