This wires two inVERTs in parallel so that the indicator light only flashes when both the left and right turn signals are flashing together.

Wiring Hazard Indicator

Here’s another great question that we we received from a customer.  They are installing a late-model OEM hazard switch into the dash of the Corvette resto-mod project.  This switch has an indicator light built into it.  They asked us how to wire the hazard indicator in this switch.  Read on to learn more.

In most cases, you are powering your dash indicators by tapping into the POWERCELL output for that function.  For example, your high-beam indicator is going to be powered from the POWERCELL output for the high-beam.  You splice off of the high-beam output wire from the POWERCELL and connect it to the indicator bulb on your dash.  You then ground the other side of the bulb.  When your high-beams are on, you have battery voltage on the bulb which indicates that the high-beam output is on.  You do the same thing for your left and right turn signal indicators.

The question pops up about what to do when you have an indicator on your hazard or 4-way flasher switch.  You can’t splice off of the turn signal outputs directly and wire them together to the indicator bulb.  If you did that, the indicator bulb would flash when either the left or right turn signals turned on.  You want the hazard indicator bulb to flash when the 4-ways are on.

There are several different ways to do this.  You could use relays to do this.  You could also build a little transistor circuit to do this.  The easiest way to control your hazard indicator light is to use two of our inVERT Mini‘s wired in series.

We created our inVERT Mini to help guys connect 12-volt switched functions to the ground-switched inputs on a MASTERCELL.  Examples of where you’d use an inVERT Mini include cooling fan and fuel pump signals from an ECU.

This diagram shows you how to connect the inVERT Minis to the turn signal outputs and the indicator built into the hazard switch.

This wires two inVERTs in parallel so that the indicator light only flashes when both the left and right turn signals are flashing together.

Simple diagram showing how to control the indicator light on a Hazard switch.

Here’s how this works.  You splice the input wires on the inVERT Minis to the turn signal outputs on the front POWERCELL.  You can do this right where you have spliced  into the turn signal outputs to drive the left and right turn signal indicators.  When either of the turn signals are on, current can flow between the MC & G terminals on the inVERT Mini.  If only one of the turn signals is flashing, the current path is blocked by the other inVERT Mini.  When the 4-ways are on, both the left and right turn signals are flashing together.  When they are both on, there is a current path through both inVERT Minis which turns on the indicator light.

There are a few warnings that you must follow when wiring this.

  1. First, the hazard indicator must be completely isolated from the switch contacts.  Check the wiring diagram that came with the switch or spend some time with a multi-meter to figure out which terminals are connected.
  2. The maximum current that flows through the indicator light must not exceed 0.25 Amps (250 milli-amps).
  3. The polarity of the light is very important if the hazard indicator is an LED.  It will not work if wired backwards.
  4. If the hazard indicator light is an LED, you must check its rating.  Most LEDs will call out either an operating voltage or a maximum forward current.  Make sure that the voltage rating is at least 12-volts.  If they specify a maximum forward current, you must have a limiting resistor to protect the LED from damage.  (Remember, V=IR.  You can do the math or give us a call with questions.)

You can download a PDF of this wiring diagram by clicking this link.

If you have questions or comments on this post, please click on this link to contact a member of our technical support team.