Toyota Yaris DIY

This mod makes the headlights turn off when the ignition is turned off, preventing one from killing the battery when accidentally leaving the headlights on. With this mod, in order to leave the headlights or parking lights on, the key will need to be in the ignition switch and turned to the on position.

Note: This modification is to be done at your own risk! Failure of the relay or wiring connections can result in the headlights turning off unexpectedly!

Parts required:

Relay – SPDT or DPDT relay (12 VDC coil, 10A contacts).
Radio Shack part number: 275-218

Female Crimp-on Quick Disconnect Terminals
.187 (3/16″) Insulated for 14-16 AWG wire (quantity 2)
.187 (3/16″) Insulated for 16-18 AWG wire (quantity 2)
.187 (3/16″) Insulated for 24-26 AWG wire (quantity 4)

Wire – 3″ 18 AWG (white/black stripe)
Wire – 3″ 16 AWG (Quantity 3 – white/black stripe)
Wire – 12″ 16 AWG (Pink, Orange, etc.)

Heat shrink tubing

Tap Splice connector (14-18 AWG)

Adhesive Velcro

Tools required:
#2 Phillips Screwdriver
Soldering Iron
Heat Gun
Wire Stripper
Crimp Tool

Overview:

The relay is controlled by the ignition switch and is used to switch the ED and T1 contacts of the headlight dimmer switch connector. The ED contact is the ground common for the headlight and parking light circuits. The T1 contact is the ground for the headlight warning circuit. A dual pole relay is required to switch both of these circuits:

1. Remove the lower steering column cover: Turn the steering wheel enough to expose and remove the two screws:

2. Remove the third screw, which is located beneath the steering column, by the tilt lever.

3. Disconnect the headlight dimmer switch connector

4. Cut the ED (pin 11 – white/black wire) and T1 (pin 10 – white/black wire) wires leaving ~1″ of wire on the connector side.

5. Extend the ED and T1 wires on the connector side by soldering and heat shrinking a 3″ piece of appropriately sized wire to the ED and T1 wires (The wires have little slack, so this provides the necessary slack.

6. Solder and heat shrink two 3″ pieces of 16 AWG wire to the ED wire (harness side).

7. Strip and crimp female quick disconnect connectors to each of 5 exposed ends.

8. Connect blank female quick disconnect connectors to terminals 1 and 2 of the relay (to cover the non-used terminals).

9. Connect the connector side of the ED wire to terminal 4 on the relay.

10. Connect the harness sides of the ED wires to terminals 6 and 7 on the relay.

11. Connect the connector side of the T1 wire to terminal 3 on the relay.

12. Connect the harness side of the T1 wire to terminal 5 on the relay.

13. Locate the pink wire (Ignition ON) on the ignition switch connector:

14. Splice the 12″ piece of wire to the pink wire with the tap splice connector.

15. Strip and crimp a female quick disconnect connector onto the other end of the Igniton wire.

16. Connect the Ignition On wire to terminal 8 on the relay. The connections should now look like the following picture:

17. Mount the relay to the back of the headlight dimmer switch connector using the adhesive Velcro and reconnect the headlight dimmer switch connector:

18. Test by turning the headlights on (with the key removed) – Headlights should not turn on, and headlight warning buzzer should not sound.

19. Insert key and turn to Ignition ON position. Turn headlight switch to ON, and headlights should now light.

20. Reinstall lower steering column cover.