some other tips for installing a sr20det into a s12.
1. Speedo drive.
Take the speedo drive pinion out of your old ca18et g/box and swap it into the sr20det g/box. Then just connect your ca18et speedo cable from you g/box speedo drive to the speedo, problem solved. Everything runs okay without the electrical signal from the sr20det electronic sender, only thing you will notice is that when you pull up that idle will drop momentarily, then pick up to normal immediately.
2. Tacho.
You need to find the 4 wires that go from your ignitor chip to your coil packs and (carefully!!) splice in 4 diodes on to each of these wires then join the ends of the diodes together to a single wire. This wire then gets connected to the 12v+ wire of your tacho.
"......used 4x IN4004 diodes connected to the coil side of the ignitor, about 3 inches from the plug is easy enough, then just joined the 4 diodes together on the tacho side and joined that wire straight to the tacho, the stripe on the diodes is towards the tacho (not sure if that is anode or cathode), and there you go......"
The input signal for your tacho is a yellow and red(stripe) wire that runs from the ECU to a small white plug that comes off the ECU wiring. Connect a wire from your tacho signal in wire to this yellow and red wire.
3. Voltage guage.
s12 signal to the guage is via a white and red (stripe) wire that runs through the harness to the alternator. There is a white and red wire on the sr20det alternator that matches this.
4. Oil pressure.
Just swap the ca18et oil pressure sender for the sr20det one, (sr20det s13's only had a light not a guage) and hook your existing s12 oil pressure sender wire up to it.
5. Temperature sender
There is a blue and black (stripe) wire that runs to the same small white plug off the ECU that carries an engine temperature signal, connect your temp guage input signal wire to this, I think the temp guage then reads correctly, but check with nebercenezer on that.
6. Various warnng lights on the dash.
s12 has a brown wire than runs to the instrument panel warning light relay to trigger these. There is a brown wire in the sr20det engine harness wiring somewhere that matches this and you need to splice this onto the s12 one before the relay. (i.e. when you turn your igntion to on these warning lights show and then when you start they turn off, (if nothing is wrong that is!!)).