Sensors & outputs Power
Relay — ISO mini
Main, pump, fan · output · Power
Standard 5-pin ISO mini. ECU low-sides ground the coil (85). The high-current path (30 → 87) never goes through the ECU. Same pinout for main, pump and fan — different low-side.
Typical parts: Bosch 0 332 209 ISO mini 5-pin; Tyco / TE ISO mini; Hella ISO mini
Note — ECU grounds the coil. Race Core wakes on B18 (5 A) and pulls 85 to ground. That is the whole control path.
Device pinout
Looking at the terminal face of the relay.
- Connector: ISO 7588 mini, 5 blades. Numbers are moulded in the relay base.
- Layout (looking into the part): 86 · 87 · 30 / 85 · 87a
| Device pin | Function | Type | Race Core | TunerStudio |
|---|---|---|---|---|
| 85 | Coil − (ECU low-side) | Low-side | A21 main / A20 pump / A12 fan | Lowside 12 / 10 / 15 |
| 86 | Coil + (switched 12 V) | 12 V | Ignition 12 V (main) or main-relay output (pump, fan) | — |
| 30 | High-current feed | 12 V | Fused battery + | — |
| 87 | Normally open output | 12 V | Load: B23 / pump / fan | — |
| 87a | Normally closed (usually unused) | Ground | Tape back | — |
Wiring notes
- Main relay: 86 from ignition-switched 12 V, 85 to A21 (Lowside 12), 30 from 15–25 A fuse at the battery, 87 to B23 + injector rail + coil rail + pump-relay pin 86.
- Pump relay: 86 from main-relay 87, 85 to A20 (Lowside 10), 30 from a 15–25 A fuse sized to the pump, 87 to the pump +. Pump current never enters the ECU.
- Fan relay: 86 from main-relay 87, 85 to A12 (Lowside 15), 30 and 87 sized to the fan.
- A 4-pin relay is the same without 87a. Fine.
Failure modes
- Main relay clicks and the ECU resets while cranking: pin 30 is fed from a small ignition fuse. The high-current path needs its own fuse at the battery.
- Pump runs with the key on and the ECU unplugged: pin 85 is grounded in the harness instead of by Lowside 10.
- Fan runs backwards or not at all: 87 and 87a are swapped on a 5-pin relay.