Fogs modified to run as DRL's on my C32

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Active Member
Jan 1, 2012
Royston, Herts
2005 E320cdi
Well my new LED HB4's and resistors finally turned up and after work I popped the car up on the ramp and swapped them out and they look great.

At lunch time today I set about hooking up the wiring to run the fog lights as DRL's it is simple and most of the work has to be done inside the engine bay fuse box I first find an ignition switched 12v to activate the trigger side of a 4 pin relay I then lay down an earth for the opposite pin on the relay this I used the Earth post just outside the fuse box then I needed an empty fuse slot to take the permanent 12v that will power the DRL's this I placed a 10a fuse in line before connecting to the relay then the final pin is the wire that needs to be fed down to the fog light units and with the use of a simple diode in line these are only needed to keep the bulb out warning system happy these need to be used the correct way round as power will only flow in one direction through them and one is needed to be fitted in line just before each light then they can be tapped into the positive side of the fog light wiring and that's it.

I might have been able to wire them directly at the LCM if I was able to find it and a wiring diagram but as I was already messing about down at the lights fitting the bulbs there was no drama wiring directly to them.

Now my new DRL's are on when the ignition is on and go off when you switch off.

Here's the diodes I use:

1N4001S 1A Silicon Rectifier | Maplin

Wiring in the fuse box:

as I was rushing I didn't get any other pictures but here's a video showing them in action:


Another little mod I carried out is to rid the horrible orange bulb look through the lenses I do this very cheaply by giving a pair of amber bulbs a dusting with silver spray this way it gets rid of the orange look and they still work perfectly.


dusted with silver spray:

How the lenses looked before:



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