2004-2009 Mazda3/MAZDASPEED3 Fog Light switch modification how-to
by Edwin Man
Copyright © 2005-2008 Edwin Man. All rights reserved. No reproduction by any means permitted.

The following instructions will allow the stock fog lights to function while only the parking lights are on as well as when the high beams are on.
This allows for increased user control over the fog lights and allow them to be used as independantly during extremely foggy conditions where the use of headlights cause excessive backglare. It will also allow maximum lighting output when you are on a dark road where you want as much light on the road as possible.

These instructions are intended for North American models only since Mazda3's in other continents do not require this modification (the fog lights work with just the parking lights on). These instructions work with all North American models (US/Canada/Mexico) with both halogen and HID headlight systems. For Canadian models, Daytime Running Light (DRL) functionality is still retained and illegally disabling that system is beyond the scope of this how-to.

Since you will be messing with important (lighting) safety equipment on your car, a solder splice method in this how-to will be used. Crimp on "butt" connectors are NOT recommended.
Required time: 1 hour
Difficulty level: Moderately Difficult
Required tools:
 Basic disclaimer: work carefully and take your time. If you screw up, it's your fault. Always excercise caution when working around electrical systems. Heat from soldering iron, heat gun, cigarette lighter, matches, etc. can cause burns!

  1. Record all radio presets and settings. Open the hood and disconnect the battery. You will have to remove the battery cover by pressing on the clips where the air scoop duct meets the battery cover.
  2. Remove the plastic cover under dashboard below where the glove compartment is. Just grab it at the edges and gently yank it off.
  3. You should now see the white "power junction box". Disconnect the small green and orange connectors as well as the large orange connector. Just flip the black levers to disconnect them. On the large connector, you will have to grab the two clips on the sides of the lever to unlock the lever for rotation.
  4. Unscrew (by hand) the power junction box and flip it down. The screws are located near the bottom edge of the dashboard; they are hard to miss.
  5. Disconnect the two blue connectors on the left and then disconnect the large green connector. The disconnection method is the same as on step 3.
  6. Unhook the power junction box from the bracket and remove the power junction box.
  7. Cut the zip tie on the large green connector and unwrap the tape closest to the connector.
  8. Locate terminal "D". It is near the zip tie bracket. There should be a Blue/Orange wire and Red/Black wire coming out of the terminal (US models; Canadian models has Red/Black only) on the 2004-2006, on the 2007-2009 there is an Orange/Green and Red/Black wire or Blue/Orange and Red/Black wire depending on whether you have HIDs or not. Follow that Red/Black wire up to where the tape was and cut it there. DO NOT cut the Blue/Orange or Orange/Green wire!
  9. Locate terminal "AC". It is in the opposite corner of terminal "D". Follow the Orange/Blue wire up to where you cut the wire and make note of it. DO NOT use the terminal "K" Orange/Blue wire.
  10. Swing the Red/Black on the connector end out of the way and then strip about 1/2" on the harness side end of it.
  11. Hold down all the wires in the harness in the position it would be when everything is secured. Now place the newly stripped Red/Black wire next to the terminal "AC"s Orange/Blue wire. Make note of the position.
  12. Using a pocket knife, peel about 1/2" of insulation on the terminal "AC"s Orange/Blue wire away. Becareful NOT to cut the wire.
  13. Twist the newly stripped Red/Black wire onto the now exposed Orange/Blue wire then solder them together.
  14. Tape the now unused connector end of the Red/Black wire off and tuck it back into the harness. Tape the newly spliced wires together also.
  15. Install a new zip tie to secure the wires to the harness connector the same way the factory did it. "Band" the harness together with tape in approximately the same location as it was from the factory.
  16. Locate the small green connector and unclip its harness from the bracket. There should be only a few wires on that connector.
  17. Unwrap the protective loom and remove the Black/Red wire (connected to terminal "X") from it.
  18. Cut the Black/Red wire approximately 1" from where the protective loom ended near the connector.
  19. Tape off the Black/Red wire on the connector end then tuck it back into the protective loom.
  20. Swing the Black/Red wire on the harness side out of the way. Tape the protective loom back in its original place.
  21. Reinstall the clip and harness back onto the bracket.
  22. Locate the Black/Red wire on terminal "W" on small blue connector. It is next to the White/Green wire and is nearest the locking lever when it is in its fully unlocked position. DO NOT use the terminal "C" Black/Red wire!
  23. Follow terminal "W"s Black/Red wire up to about 3/4" from the blue masking tape a few inches from the connector then cut the wire.
  24. Swing the Black/Red wire on the connector end out of the way. Strip 1/2" of the Black/Red wire on harness end.
  25. Strip 1/2" of the Black/Red wire that was part of the small green connector's harness.
  26. Cut about 2" of 1/8" heat shrink tubing and insert it into the Black/Red wire as far as away as possible from the exposed end.
  27. Twist the two newly stripped Black/Red wires together then solder them.
  28. Slide the heat shrink tubing down to the splice point then use a cigarette lighter to shrink/melt it in place. Ensure your flame is AWAY from all other objects!
  29. Tape off the Black/Red wire on the connector end then tuck it back into the harness.
  30. Reconnect the large green connector to the power junction box then the two blue connectors. Connectors MUST be seated flush with the sockets on the power junction box!
  31. Reinsert the power junction box into the bracket then flip it back up and tighten the two screws to resecure the power junction box.
  32. Reconnect all the other connectors in the same method as step 30.
  33. Reonnect the battery and test to make sure the fog lights work in ALL light modes on the light controls.
  34. Reinstall the plastic panel.