WewLAddiE

Thought this would be a fun addition to the mounds of information and writeups on here, especially for the s4 guys...

Today I was looking around trying to figure out why my shift light only goes off at low RPMs, Only come to find its supposedly a "Gas saving measure", if i wanted to save gas I wouldnt be driving an RX7. So i decided to see if there was a way to adjust when it went off, only to find zero information on the matter. Some careful thinking later, I came up with what you see here. The mod wires the light bulb to the power and ground of the buzzer (my buzzer is dead and doesnt work anyways), so that not only does the light go off when the RPM buzzer is supposed to, but, as you'll find in other threads, you can actually adjust when this shift light comes on.

Tools:
- Soldering iron and all the fixins' (solder, flux, etc.)
- wire, i used 16 gauge ( i think... ) but i dont think it matters much
- light bulbs. The shift light and other dash lights are #158 lightbulbs, you can get them from your average autoparts store... not a bad idea to have a few extra

Part (1) the PCB


This is the back of the gauge cluster as you'll find when you pull it out of the car, the big red circle is the location of the shift light, To the right are the positive and ground terminals for the RPM buzzer, these two spots are where you're going to solder your wire to

Part (2) Wires and stuff


Sorry to say, but i didnt manage to take pictures of the soldered joints, i can upload some tomorrow (buying a new buzzer to try and wire in) But ill attempt to describe the process.
There are two smallish tabs on the light bulb side of the black holder. Take the light bulb out and bend the tabs upwards, I soldered the wires with the copper side facing down (towards the base of the black holder) to the tabs then bent the wires down to come out the correct side. You may have to experiment with the direction of the wires as i had to take a bit of careful work melting plastic and changing the size of the tabs that hold the lightbulb to the pcb in order to allow the lightbulb to insert back into the pcb properly

Then i soldered the wires to each of the buzzer contacts. Keep in mind your wires shouldnt contact the normal lightbulb contacts on the pcb

Part (3) The adjustment

This is Shift buzzer potentiometer or "pot" for short... This is the adjustment i have on my car right now turned slightly counter-clockwise from the stock position, the light comes on around 6400rpm and thats perfect for me as I wanted a buffer between when the light came on and when I was at redline. If you want to keep the light to come on at 7000rpm redline you should leave this adjustment alone. Counter-Clockwise turns the activation lower on the rpm range, and clockwise will raise it.



Blown-up high contrast image of the adjustment, the red line is where the stock adjustment is set.


And finally a video showing it in action.

Thats all, thanks for reading. Have fun.

WewLAddiE

I wanted to post a quick update. Ignore the modification to the socket and purchase a wired T3.25 Wedge base socket: https://www.superbrightleds.com/more...red/1150/2737/

The plastic casting is low-quality and needs a little trimming to work smoothly, but its way better than the melted-plastic mess that I had above.