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The hazard switch and indicators often cause problems in defenders, most commonly the indicators stop working, but the fault is actually with the hazard light switch.
This post aims to explain how the hazard switch works, why it's malfunction stops the indicators working, and how to test for and diagnose the fault.
To get to the back of the hazard switch, remove the two screws and pull the switch panel out. you'll then see this.
The multi plug has 7 wires going into it, there's also the Black (red trace) and Black wires, which are connected directly to the switch body. these are for the indicator in the switch itself.
Black(red) - indicator supply
Black - earth
Remove the multiplug, you will then see the two sets of pins, x3 and x4, top and bottom (as viewed in the photo, not as mounted in the dash).
The top set are concerned with powering the flasher unit, the bottom set dictate what the flasher unit actually lights.
This picture shows the 4 wires that connect to the bottom set of pins
And this picture shows the 3 wires that connect to the top
To make things easier to see, here is a schematic of the switch.
With the Hazard switch in the 'off' position
'Suppy to flasher' is connected to 'Light switch supply' - which comes on with the second click of the ignition switch
With the Hazard switch in the 'on' position
'Suppy to flasher' is connected to 'Permanent Supply' - 12vDC
*Flash* is connected to 'Left Indicators', 'Right Indicators', and the 'Switch tell-tale'
What this means is, if the switch is faulty, the flasher unit doesn't get a power supply, so it can't flash the indicators via the indicator switch on the column.
You can test the switch using a multimeter (continuity or resistance), or test lamp. You can also test the vehicle wiring as follows.
You will need a fused piece of wire (or test lamp), you don't want to risk a dead short if you get it wrong.
This is what i made to test the wiring, the lowest value fuse i had was 5A.
If you link 'permanent supply' (purple) to 'Left indicators' or 'Right indicators' the indicators on that side should light, constantly though, not flashing. this proves the bulb wiring is ok and you have supply to the loom plug.
If you link 'permanent supply' (purple) to 'supply to flasher' (light geen), the indicator stalk switch should work the indicators as normal (flashing). The indicator switch is connecting *flash* to 'Left Indicator' or 'Right Indicator' - the wiring is duplicated at the stalk switch. If you want to make a seperate link wire you can replicate the stalk switch action at the loom plug as well.
You can repeat the two tests above, using 'Light switch supply' instead of 'permanent supply', the ignition switch will need to be on the second click.
'Switch tell-tale' is the live supply to the bulb in the switch housing, it is grounded by the seperate black wire connected to the switch body.
