How should electric fans be wired with a Terminator X / LS swap ECU?
Most aftermarket EFI systems have cooling fan outputs. Use them to trigger relays, never to power the fans directly.
Speedway's recommended dual-fan setup:
- Two relays, one per fan. Each fan's positive goes to its relay's output. Relay coils get switched power; the relay power feeds get fused constant power.
- Trigger: the ECU's fan output (or a thermostatic switch) grounds the relay trigger side.
- Don't run both fans off one standard relay. Two fans starting at once can blow the ~30 A fuse on a standard relay. A single high-current relay works if you're short on space, but costs more.
- Staging: you can run one fan on temperature and the second on A/C compressor engagement or a manual switch.
Confidence: medium — sources disagree or are limited; check the sources below.
Community discussion
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Sources
- How to Wire Dual Electric Cooling Fans — Speedway Motors