Sometimes you want to greet or warn an oncoming car or fellow Mazda driver by flashing your headlights. In a "normal" car you just pull the lever on the steering column, but with my Miata from '90 that doesn't work. The lights switch on but don't open, so this has little effect.
Miata.net has a simple description to get this working. You simply have to fit a diode into the wiring harness. This allowes for the current to flow in only one direction. So when you pull the lever on the high-beams the 'open-close' circuit is also activated.
I got myself a diode at the 'radio center' in Utrecht. Miata.net prescribes a BY127, but a 1N4007 is technically identical.
To fit all this, you must first remove the kick-panel under the steering column (2 screws), and the cover around the levers (4 screws). This releases the cable harness and the ingnition switch:
you then have to follow the wiring harness that comes out of the steering levers. To make working a bit easier, I disconnected the connector.
The diode must be placed on the connector on the "car side". So the "female" side of the connector. The diode must be placed between the white / blue (white wire with a blue line) and the red / white (red wire with a white line) wires.
I bent the ends of the diode and pushed them in as far as I could. It should then touch the connectors inside the plug. Also pay attention to the line on the diode and on the picture. This is the way it has to be fitted and not the other way around!
After this, reconnect the connector, fit the kick-panel and you're done!
PLEASE NOTE: the colors and wiring harness on the later years and on the Canadian models differ. On a European MX-5 you can "signal" but the lights stay up for quite a long time. So pay attention to which modification you must perform!
Flash To pass on a European MX-5:
On a European MX-5 the lights go up and stay up for a few seconds. The time they stay open is determined by a condensor inside the relay. The heavier the condensor, the longer they stay open.
What is a condensor?
You can compare a condensor to a small battery. When the power comes on the condensor is charged and the cicuit is activated. When the power is switched off, the condensor drains of its charge and when it is empty the circuit switches off. The time it takes to drain the condensor depends of its capacitiy. The capacity of a condensor is expressed in µF (microfarad).
What do you need?
1 new condensor, scissors or pair of cutting pliers, small soldering iron and some solder. The condensor can be bought at an electronics store or online. What you need is a condensor of 6,8µF (at least 12V). They are not very expensive (think quarters/pennies, not €/£/$).
Where is this relay?
The relay is located under the dashboard at the driver side. When you look under the dash you can see a few to the left of steering column. It is the one mounted furthest forward. When you hold it and switch yourm lights on you can feel it click. After you have removed the connector (press the tab!) you can take it off its mount. It can be quite tight but a little patience and wiggeling should make it come loose.
The housing says:
B481 67 7COB
What to do?
Now pry open the housing and carefully take out the print that is inside. This can also be quite tight.
Put it on your table/workbench with the connector towanrds you. The condensor should be at the top left where it says C2. It is soldered with to tabs. I you look carefully you can see print on the condensor. Besides the value (100µF) you will also see a bar/line with oval markings. On the new condensor you can find the same kind of markings. It is important to fit the new condensor in the same way as the old one.
The rest is self explanatoy, remove the old condenser, fit the new one, and fit everything to the car.