How it works
Each shift light is just an ECU output that switches on once engine speed passes a set RPM. With three lights you can build a countdown: a first warning, a second closer to the shift point, and a final "shift now" light. The lights are independent, so each one gets its own output and its own activation RPM.
Wiring tab
- Number Of Shift Lights: choose one, two or three.
- Shift Light 1, 2 and 3: pick the output for each. Any free output will do, and a DPO or stepper output is the usual choice.
- Active State: sets polarity. On the default, Low, the ECU grounds the output while the light is on, which suits a lamp or LED fed with 12V on its other side. High inverts that, grounding the wire while the light is off.
ECU outputs switch small loads. An LED indicator is fine directly, but a bright incandescent lamp or a large light bar should go through a relay.
Shift Light tab
Enter an Activation RPM for each light. A light comes on once RPM rises above its value.
| Light | Role | How we set it |
|---|---|---|
| Shift Light 1 | Early warning | A few hundred RPM before the shift point |
| Shift Light 2 | Get ready | Closer again |
| Shift Light 3 | Shift now | At your shift point, allowing for your reaction time |
Your ideal shift point comes from a dyno sheet: shift where the power in the next gear is higher than the power you'd make staying in this one. Remember that you react a moment after the light comes on, and the engine keeps revving during that time, so the last light usually wants to be slightly early. Keep all three below the rev limiter.
Troubleshooting
| Symptom | Usually |
|---|---|
| Lights on all the time, off at high RPM | Active state inverted for your wiring |
| Light never comes on | Wrong output assigned, number of lights set too low, or no 12V feed to the lamp |
| Lights come on in the wrong order | Activation RPMs or outputs swapped |
Running a Haltech dash? Many dashes have their own shift light displays, so compare that option before running separate lamps. Other functions on this menu include air conditioner control and boost control.
