Installing a diode

[Dave_EH]

I have just wired a relay to my ignition wire to utilise 12 volts on my electronic dizzy.

I cannot switch the motor off using the key now.

I have been told that the wire from the alternator to gen warning lamp runs enough voltage to hold the relay open and causes this problem.  The remedy is to fit a diode to the genwarning lamp wire.  

Could someone please assist me with some more indepth instructions on how to perform this task>

Cheers
Dave

[Ed]

grab a diode, which only allows current flow in one direction.

solder it in place in the desired position, put heat shrink over the soldered joints.

test out its polarity using a test light or multi meter.

easy?

Ed