Tired of only being able to turn the fog lights on with the low beams? The following modification I performed on my 04 Evo piggybacks the stock fog lamp system without cutting any wires and allows the fog lamps to work independently of the low beams. I have looked at the wiring schematics for 03 - 06 Evos and they function the same and use the same switch, so this mod will work on them all.
This modification requires building a small simple circuit with parts availible at your local RadioShack. The circuit is then installed under the dash with 4 simple wire hookups.
Note: This circuit can be switched on and off repeatedly, however once switched off, there is about a 3 second delay before you can switch it back on as the capacitors discharge.
The Circuit
Parts needed:
1 - MPS2222A or similar small-signal NPN
1 - IRF510 n-channel MOSFET
1 - D1 1N4001 silicon diode
1 - R1 1M 0.25W
1 - R2 4.7M 0.25W
1 - R3 10k 0.25W
1 - R4 330k 0.25W
1 - C1 220nF ceramic disc, polyester or mylar film
1 - C2 100nF ceramic disc, polyester or mylar film
2 - 12v relays
Misc Wiring (red, black, white and green used below)
Project Box
1 - Circuit board
Once you have aquired the parts build the following circit:
Note: when wires intersect WITHOUT a dot there is no connection.
There are 4 external connections to this circuit. One connection to ground (white), One to the fog lamp relay's ground (black), one to the fog lamp switch (yellow) and one to a 12v power source(red) (parking lamps, ignition.... this is the power source that will determine when you can switch on your fogs)
(ignore the small red jumper on the left, it was not used)
The extra pin on each relay was cut off as it was not used.
Here is my completed circuit installed into a small project box
Installation
1) Find a suitable location under the dash to mount the box
2) Connect your ground to a chasis ground (white wire from box)
3) Remove the plastic facia from in front of the speedo to access the back of the fog lamp switch
4) Tap into the top wire of the switch (with the yellow wire from the box) - this wire sees ground when the switch is depressed (this was the correct wire on my 04 Evo. I need confirmation that the same switch is used over all the years)
5) Connect your 12v source wire (red) to a wire that has 12v when the ignition is on. This will keep you from leaving the fog lamps on when you turn the key off. You could also connect this wire to the parking lamp power wire or the dash lights. This circuit is VERY low current and will not effect any of the existing electronics.
6) Run the wire labeled "to parking lamp relay" (black) into the engine compartment to the fuse box on the drivers side. The relay pointed to in the picture is the fog lamp relay:
7) To turn the lights on we need to show this relay ground. The contact pointed to is the contact we want our wire connected to. As can be seen in the second picture below here I soldered my wire straight to the relay pin that rests in that contact.
However a modified fuse tap can also be used:
Make sure it is placed in contact with the proper contacts and that it cannot short to any other contact after the relay has been installed (Make sure its firmly in place)
8) Reinstall the relay:
9) Reassemble your dash and pat yourself on the back, its done!
You now have fog lamps that work when YOU want them to work
All pictures located here:
http://www.haughs.net/gallery/v/toys/evo_viii/fog_mod/
but if there is enough interest I could probably work something out, but it wouldn't be an overnight thing.
i don't understand the schematic you posted on how to make this circuit, wish i did! i can follow the rest of the install, just wish there was another way for you to show how to build the circuit.
. This could be a good side job for you, I am sure a few people here would be interested.
