Anytime Fog Lamps

This is an illustrated HowTo for modifying the engine compartment fuse/relay box such that the fog lamp switch will always turn on the fog lamps in a 2006 V6 4WD Access Cab Toyota Tacoma.


Fog lamps on; headlights off—can't do that with a stock Tacoma.

I find it odd that on a stock 2006 Tacoma, the fog lamps can only be turned on when the dim headlights are on. If you turn off the headlamps, the fog lamps go off as well. Also, if you turn on the high beams, out go the fog lamps. Now why would I want the fog lamps on with the brights or without the headlights altogether? I don't know. But preventing me from doing so seems odd. Anyway, the modification is very simple.


The engine compartment relay/fuse box before any modifications were made.

I've marked the relay which controls the fog lamps in the above image. The reason the fog lights won't come on whenever you press the button on the dash is because the fog lamps button grounds one end of the relay coil, but the other end of the coil control is connected to the output of a relay which is only activated when the non-highbeam headlights are on. To get the fog lamps to come on whenever the button is pressed, we simply connect pin 1 of the relay to the battery.

Remove the fog lamp relay and bend pin 1 as shown below:


Pin one bent at 90°

Next, you'll need an "Add-A-Circuit" dongle. They look like this:


The ATO Mini Add-A-Circuit

Basically, this thing plugs into a mini fuse socket and provides slots for two fuses. The lower slot is for the original fuse. The upper slot is for the new circuit, and connects the left leg of the fuse connector (as shown above) to the wire with attached butt connector. I installed the add-a-circuit in the DOME fuse position, as it is only rated for 10A circuits (DOME is a 7.5A). Also, there were a limited number of fuses in this enclosure that were connected directly to the battery and that you could plug the add-a-circuit into without the wire attachment getting in the way of some relay.

The add-a-circuit comes with a selection of mini fuses. The Tacoma stock fuses won't fit in it (as they have no legs) so I put one of the provided 7.5A fuses in the lower slot for the DOME circuit, and then added the provided 5A fuse in the top slot for the fog lamp relay driver circuit. This is probably overkill and I could have used the provided 3A fuse (or even smaller, though the 3A is the smallest provided).

In the free end of the butt connector, I crimped a short (5cm) piece of 16 gauge wire, and on the other end of that wire I crimped a female quick disconnect that fit perfectly on the bent pin spade of the fog lamp relay. Then it was just a matter of plugging the relay back in, and placing the add-a-circuit into the slot for the DOME fuse. Here is the final product:


Final installation

With this modification, the fog lamps will come on when you hit the fog lamp switch, regardless of the state of the headlights—even if the truck is off.

Gripes:

If they had just given me 2 more inches of wire on the dongle, I could have cut off the butt connector and crimped the wire directly into the quick disconnect. Oh well.

The Add-A-Circuit dongle doesn't sit as tight as I'd like in the fuse slot; I'm afraid that during off-roading it might come loose. However, as it would only affect my fog lamps and dome light, it's not a safety issue (the alternative fuse to use was the engine computer fuse!).

Also, the Tacoma won't let you leave your headlights on when you leave the truck (if the lights are on and the car is off and you open the door, it kills the lights). But with this hack, the fog lamps will be left on to drain the battery.

Finally, there is no indicator inside the cab that the fog lamps are on. Generally, at night, this is obvious. But if I accidentally hit the switch during the day I might miss it. So I'd like to rig up an LED on the dash somewhere that indicates the fog lamp state. Future project.

Parts

  • Mini Add-A-Circuit $5.99
  • Female Quick Disconnect $0.10
  • 5cm of 16 gauge wire $0.05
    -------------------
  • Total: $6.14

Tools & Supplies

  • Crimper/Stripper

©2006 Mouser Williams