Installing Front Fog Lights to OEM Rear Fog Light Switch - 1993 HDJ80

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May 22, 2016
Los Angeles
Goal: The goal is to wire the new front fog lights (55w H2 Cibie 95s) into the OEM fog light switch that was installed in my European HDJ80. This switch controls the rear OEM fog lights mounted on the tailgate. This switch and the rear fog lights ONLY WORK when the headlights are turned ON.

*This was my first time wiring anything… I learned a ton with trial and error and just diving in. I have no idea if my wording is correct, but ill do my best.*


Rather than splicing into the rear fogs, I plan to instal a designated 30A relay that will work solely for the new fog lights. This relay needs to be triggered by the OEM switch before it can send power to the front fog lights.

  • The OEM switch is a Negetive Trigger switch (this seems to be the case with many Toyota switches). Rather than sending out a positive signal when the switch is ON, it activates the ground. So, the only wire that changes signal when the switch is pressed is an outgoing ground. In my case it was the Red and Blue wire. In order for our switch to work for our relay, I had to splice into this switched ground and run that to the (85) *ground* pin on the new 30A relay.
  • For the (86) pin *positive side of the coil*, i found that I needed to run this from the corner running light. Power doesnt matter, as long as it gets a signal. Why? I had initially run the (86) and the (30) Pins both directly from the battery (with a 30A fuse). This presented a problem when the headlights were off. Whether the ignition was on or off (motor running or not), there was always enough power being set into the relay to make the relay act funny. It would click on randomly. Once the headlights were tuned on, however, everything would work as it should. In order to solve this, I spliced into the cover running light rather than the battery for (86) pin in order to eliminate any power being sent to this pin UNLESS THE HEADLIGHTS WERE ON. I used the corner light because it is on no weather there are high or low beams.
  • The (30) *power in* pin was run straight from the RH (Passenger side in LHD 1HDT 24V starter HDJ80) with a 30A fuse. *DO NOT PULL ACCESSORY POWER FROM THE LH BATTERY IN THESE 24V STARTER TRUCKS*
  • The (87) Pin is your output. I ran this to the fog lights. Each fog light is grounded individually to the fender.

After tidying everything up, everything works as it should. WIth the headlights on, I can press the OEM button and the front and rear fog lights will turn on at the same time. The in dash light turns on to notify me they are on. And this works with high or low beams.

Final Wiring Diagram:

OEM Switch for rear fog lights:

Corner light splice—in. I spliced into the green + wire on the loom for the corner running light:

Keeping things tidy with conduit:


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