12 replies to this topic

[Vince208]

Hi, How do you use s multimeter to confirm which connector on the coil is the positive? The coil seems to work the same whichever way around I attach the wires from the car, but given I want change to electronic ignition, Ok need to determine for definite which out put on the coil is which. Thanks.

[nicklouse]

It does not matter really. But the casing will be marked.

[unburntfuelinthemorning]

And if it's not marked maybe just get another one that is.

[Vince208]

Sorry, I wasn't clear. The coil is marked positive and negative. What I need to test is which wire from the loom goes to which terminal. This doesn't matter for normal points, but it the wires have to be the correct way around when converting to electronic ignition.

[Chris1275gt]

Look at the wiring diagram for the model of mini you have that should do the trick.

[cal844]

The coil should be marked 12v or + for the input positive side.

[viz139]

Depending on exactly what year and model mini it is and what brand the electronic ignition is generally the white wire from the loom goes to the + on the coil and red wire to ignition modual and the white/black wire in loom goes to coil - and black wire to ignition modual.

[Vince208]

Thanks. The car is 55 years old (although the engine is an A+, and I'm not confident relying on the wire colours as they are not clear. With both coil wires disconnected, one is live and the other isn't. Can anyone confirm from this which is the positive?

[floormanager]

Is the car positive or negative earth?  If negative earth, the ignition feed (12v constant live) goes to the + terminal.  The negative terminal goes to the contact breaker

[viz139]

If the car is 55 years old it is probably positive earth. If you are changing to an A+ engine with an alternator it will be negative earth as will the A+ electronic ignition. Convert the car to negative earth

[Chris1275gt]

As the wire to the distributor from the coil is short and goes nowhere else pull them all off get your tester on buzz it would take you 2 mins to find which one is the - to the distributor

[Ethel]

If the car is 55 years old it is probably positive earth. If you are changing to an A+ engine with an alternator it will be negative earth as will the A+ electronic ignition. Convert the car to negative earth

This is the bottom line - the diodes in an alternator dictate it has to be all wired -ve earth really.

 

Polarity doesn't matter to the coil, but having the primary and secondary windings the right way round does. The -ve terminal  is  on the primary and goes to the distributor. Though it's possible transistorised ignition modules won't like that.

[GraemeC]

Are you asking how to use the multimeter to find which of the 2 wires is live when the ignition switch is turned on?

If so, set the multimeter to DC Volts (if there are options then 0-20V or similar)

Then hold the black probe to an earth point such as the cylinder head studs

Now (with the ignition turned on) touch the red probe onto each wire in turn and see which records an output on the meter - that one is the ignition live.