audifan
A2OC Donor
The auto headlight switch as we all know does not come with a functioning tel tale for the rear fogs. This is now a mot failure ( yes some testers either know the switch cannot be accidentally left on rear fogs or do not check either way a gamble. I tried to find a way to use the existing LED that is used only to indicate the switch is in programming mode but failed. So this is what I did.
I removed the auto switch and its sensor from the car to take it apart. On the rear ( on my switch ) there were 2 small screws holding the wiring part to the mechanical part of the switch.
I took these 2 screws out and slowly and carefully pulled them apart. This left the internals of the mechanical switch exposed.The other half had the board for the illumination and tell tales.
The switch half has long channels the light passes through from the leds to the fascia icons with plenty of space for another led. Great news.
I already bought prewired 12v 3mm green led as front fogs illuminate in green although amber is the more common colour. The led was sourced from Amazon ( pack of 20 ) and looked how to wire it in.
The first issue was how to get the wires from the mechanical half to the electrical half as no obvious path for the wires could be seen, so I cut a 3mm square out of the switch on the edge next to where the rear fog tell tale would be fitted. The led was placed in the long channel for the rear fog and the wires passed through the newly cut slot in the casing.
The 2 halves of the switch were carefully reassembled and the 2 screws refitted.
The wiring was run externally along the body of the switch and passed into the connectors block through a small hole which was used for the light sensor on my switch.
Now to wire the leads into the pins on the switch. The red led wire was secured with a small blob of solder to the NSL pin on the switch and the black wire again soldered on this time to pin 31. These 2 pins are opposite on the diagonal as you look at the switch.
The switch was temporarily reconnected to the car loom to test it. I now have an auto switch that does everything and now has a working tell tale for the rear fog.
Did not take any picture of the dismantling or wiring only the finished result.
Switch refitted
Ignition on
Side lights on, notice the rear fog illumination not as good due to the led blocking part of it
The front and rear fogs on
Front fogs only on
Better shot showing less bright rear fog icon.
I removed the auto switch and its sensor from the car to take it apart. On the rear ( on my switch ) there were 2 small screws holding the wiring part to the mechanical part of the switch.
I took these 2 screws out and slowly and carefully pulled them apart. This left the internals of the mechanical switch exposed.The other half had the board for the illumination and tell tales.
The switch half has long channels the light passes through from the leds to the fascia icons with plenty of space for another led. Great news.
I already bought prewired 12v 3mm green led as front fogs illuminate in green although amber is the more common colour. The led was sourced from Amazon ( pack of 20 ) and looked how to wire it in.
The first issue was how to get the wires from the mechanical half to the electrical half as no obvious path for the wires could be seen, so I cut a 3mm square out of the switch on the edge next to where the rear fog tell tale would be fitted. The led was placed in the long channel for the rear fog and the wires passed through the newly cut slot in the casing.
The 2 halves of the switch were carefully reassembled and the 2 screws refitted.
The wiring was run externally along the body of the switch and passed into the connectors block through a small hole which was used for the light sensor on my switch.
Now to wire the leads into the pins on the switch. The red led wire was secured with a small blob of solder to the NSL pin on the switch and the black wire again soldered on this time to pin 31. These 2 pins are opposite on the diagonal as you look at the switch.
The switch was temporarily reconnected to the car loom to test it. I now have an auto switch that does everything and now has a working tell tale for the rear fog.
Did not take any picture of the dismantling or wiring only the finished result.
Switch refitted
Ignition on
Side lights on, notice the rear fog illumination not as good due to the led blocking part of it
The front and rear fogs on
Front fogs only on
Better shot showing less bright rear fog icon.