Wiring Turn-Signal Indicators with ISIS...

We received two related questions this week about turn signal indicators.  The first question was how to wire the turn-signal indicators on the dash.  This is very simple.  Essentially, you are going to splice off of the turn-signal outputs on the front POWERCELL and bring these connections back to the lights on the dash.  Typically, the left and right turn-signal outputs on the front POWERCELL are brown and violet wires respectively.  The dash indicators, whether they are incandescent or LED, pull very little current.  You can use a 22-AWG wire to make this connection. 

The left & right indicators on the dash gets power when the POWERCELL is supplying power to the left or right turn signal bulbs.  This is pretty simple. 

We had another customer with a late 1960's British car who had an interesting question.  He only has one turn-signal indicator bulb on the dash and wanted to know how to wire that into ISIS.  Essentially, the bulb is supposed to flash when either the left or right turn-signals are on. 

With ISIS, this is a very simple problem to solve.  You are going to wire the turn-signal indicators just like you would if you had independent bulbs.  The big difference is that you are going to connect the wires from the left & right turn signals to the same terminal on the indicator light.  But, you need to put a diode between each output wire and the light.  Remember that a diode acts like a check valve only allowing current to flow in one direction.  Without the diodes, all of the turn-signals would turn on a the same time if there was no way to block the current from one to the other.  The diode eliminates the cross talk from the left and right sides of the car.  Check out the new application note on the http://www.isispower.com/ website. 

The diode can be any blocking or rectifier diode.  A popular part number is 1N4001.  These are available at any Radio Shack or can be purchased online from companies like Mouser and Digikey.  Note that the orientation of the diode in the circuit is important. 

You can download this schematic from our reference library here.