My homemade rear foglight indicator


foglightIn Belgium we are obligated to have a rear fog light on the car.  Since I didn't want to cut the rear bumper I looked for the smallest one I could find and hung it under the bumper.  Then, to make sure I don't let it on all the time, I fabricated a custom foglight indicator.  Originally, my car didn't come with an ABS, so I decided to convert the unused anti-lock indicator to a foglight indicator (bottom left position on the instrument panel). 

220kph versus 140mph speedo, they are interchangeableThis modification is not very difficult, but it does require modification of the printed circuitboard on the back of the instrument panel.  As I had to take the instrument panel out anyway, I also swapped the 140mph speedo for a 220kph speedo.  If you look carefully at the photo, you'll notice that there are different oil pressure gauges too.  The US speedo has an lbs/psi² gauge whereas the Euro/Japanese speedos have an kg/cm² gauge.  Some gauges don't even have numbers on them.  I believe these are the 94-on fake oil pressure gauges?

BTW, all speedos of the miata, mx5 and eunos are interchangeable.  This means that you can put a 140mph, 180kph or 220kph speedo in any car without problems, they'll all work.  One thing's important, if you car has cruise control, then the speedo has an pickup at the back.  So if you swap speedos, make sure to transfer this pickup.  There's only 2 screws to undo it.


this is the original black plastic thingyhere you can see where I added the foglight symbol (bottom left)The different signs for the indicators are all on a little black plastic, inside the instrument panel.  I simply cut the anti-lock sign out and glued a foglight sign in place.  The left picture shows the original.  On the right one you can see clearly where I glued the foglight sign on.  The pictures are not very clear, but it was very difficult to scan these in.


the final result, nice round foglight sign...Here's the final result.  Of course, when I added the abs, I had to put the ABS sign back in and redo the entire project...  Since there were no more unused indicators I had to give up the seatbelt warning indicator (bottom row, second from right).  The buzzer is still there, so I don't mind really.


This is how it's done:

Remove the access panel under steering wheel (2 screws).
Remove the 2 screws on the underside of the instrument panel housing.  To remove it, just grab it and give it a good pull towards you.  It should just pop out.  This gives you access to the instrument panel.  Remove the 4 screws.  Then disconnect the 2 connectors and the speedo cable at the back.  The panel can now be taken out.

Remove the plexi from the instrument panel.  It's just clicked on with some plastic tabs.  Gently press them and lever the plexi away.  Underneath you will find a black plastic with all the signs for the warning lamps on it (pic on top of this page).  Take it out and cut out an unused symbol (like abs, seatbelts, washer bottle fluid level etc).  Then just glue a foglight indicator over the hole.  Since the oem symbol of an Euro mx5 is rectangular, it's best to use one of the middle symbols.  The others have a round cutout in the dashpanel, which means that the symbol needs to be modified.  I put a round sticker to the back of the sign, made the uncovered part black and removed the sticker.  This way only a round part of the sign lights up.

Al that needs to be done now is to modify the printed circuit board to make the lamp come on when the foglight is on.  I found that most of the bulbs on the circuit board are connected to a permanent 12V.  This means that they go on by applying earth to the other side.  But since the foglight switch delivers 12V when pressed, you can't use it to make the lamp go on, you need earth to make it go on!
To do this you could tap into the wire going the foglight and use a relay to convert the 12V to earth.  Then just cut the circuit on the circuitboard and solder the wire from the relay to it. 

If you don't like relays (like me, they can only fail...),  cut both circuits.  Then connect one circuit to earth (there's an earth bolt on the circuit board for this) and the other one to wire of the foglight switch. 

One important thing: when you cut the circuits, there's a chance that at the same time you cut a circuit which goes to another bulb so be careful.  Oh, and use a 15W soldering iron, a 40W will instantly burn through the printed circuit board.  Don't ask how I found out...


M1's were prewired for the fog light switch. The plug is "parked" in a dummy connector on the back of the blank switchplate. If you can't see it, pull the cover plate below the steering wheel and peek up around the back of the switch.

The existing wiring will do what you want. When the switch is "on" and the headlights are on, power is available at a single pin connector on a GRN/YEL wire below the relay box near the firewall. You can use this power to run low wattage fogs or use it to control a relay for high wattage bulbs.

As far as the wires on the switch go, two pins handle the power to the connector on the G/Y wire (R/B into the switch, G/Y out). The others (one R/B, the other R) are used for switch illumination in parallel with the other switch lamps in the car.