Wiring cab accessories such as fog lights

*This post is written by Kristiaan Nugteren and first appeared in the VOLT group on Facebook.

The purpose of this is to make the following improvements:

  • Higher performance from original front lights
  • Adding fog lights in a save way
  • New accessories don’t put additional stress on original wiring
  • More power available for power hungry accessories like radio

As the pictures show there is a power increase of 32% on low beam, and a 23% on high beam!

It’s not very easy to say how much improvement in actual light this adds. From what i have been reading a slightly higher voltage will increase lumen production by a very much higher percentage.

As the numbers show, the voltage drop in the original lighting is quite high. These measurements where done on a LHD vehicle on the left lamp (with the shortest wiring). The voltage drop may vary for every vehicle since these things are old and not all switches/contacts wear down the same. As far as i have found there are no relays in the original lighting circuit. It’s just old school hand operated switches.

Since the voltage at the bulbs is so much higher the bulbs may actually run at a higher voltage than they were designed to do. If I’m not mistaking they are designed to run at 13.2V. A higher voltage will definitely lower the lifespan of you H4 bulbs. be aware of this

Recently i posted about my upgrades to the wiring around my starter battery. This included new additional wires to my dashboard to serve as a better power source for my lighting.
None of this modifications mess with the original circuits. You only need some add some signal wires for the relays. The old circuits will stay operational.

In the attached pictures you can see my configuration. Basically its made out of the following components:

  • Fuse/relay box from Aliexpress
  • 4mm2 wire fused at battery to new fusebox
  • Another 6mm2 wire for other electronics e.g radio, usb. etc
  • 1 relay relay operated by keylock switch on/off all accessories
  • 1 relay connected to light switch to power front lights
  • 1 relay connected to high beam swich to switch between hig and low beam
  • 1 relay connected to high beam switch to power high beam while lights are off (signaling)
  • 1 relay to switch fog lights activated by additional switch powered by normal light switch
  • Fuses for all the different circuits
  • New 1,5mm2 wiring harness running form fusebox to all front lights

Please be aware that these mod’s need to be done the right way! Especially the wire termination and placement of all the wires. If you don’t know how to crimp a connector the right way, or position the wire at the wrong place, this can not only lead to malfunctioning circuits, but it can also be a real fire hazard! Also use the right crimping tools, and don’t save money on good connectors and additional insulation.
The fuse box that i picked only supports 1,5 to 2,5mm2 wiring with 1 wire per terminal. I crimped the 4 and 6mm2 wire anyway, and also did double wires. Next i soldered everything and added heat shrink. I’m very familiar with these things, but be careful with this.

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