Using a 2003 WRX wagon donor with a ver7 EJ207 engine and Looks
Like they sent a ver 8 ECU. Only one fan ever turns on and based on wiring diagram it’s the sub fan. That could be me just plugging in them backwards, but none the less only one fan ever turns on. No over heating issues it stay right at the bottom of the lines of the acceptable range. When I connect the green test plugs both fans cycle on. I deleted the A/C wires, but tried my best to not cut back to another system. Is that the issue? As I see it the only wire that intersects is the Gor wire. Aren’t both fans supposed to turn on? Do I try to locate the A/C switch as when turned on should put both fans on low speed. Did I cut the low speed wired for both, not sure it’s quite frustrating. Based on this schematic what would I do to wire in a switch to control the fan that is not working to be a low/ high operation?
The ECM has 2 control wires, E17 (YG) and E28 (GR). Each can be grounded or open, in which case the circuit drives it to 12 volts. They provide 4 fan settings based on other inputs, such as engine temperature and AC activation. They control 4 relays which control the fan speed on the two fans. Here’s how it works.
You can verify this operation by unplugging F45, starting the engine, and grounding F45 GW( E28) to turn only the main fan on low, grounding F45 RL (E17) to turn on both fans on low, and grounding both GW and RL to turn on both fans high. If this works, the issue is in the ECM. Note that the engine has to get pretty hot to turn on both fans. Perhaps you haven’t gotten it hot enough. Mine got that hot while I was trying to get the air out of my cooling system and the needle went to the red area.
If you have cut all the AC wires like I did, the ECM doesn’t know to turn on the ECM when the
AC is running. I added this circuit to fix that for my AC system. You could do this too with 2 diodes and a switch to ground to turn on both fans to high.
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