FANC (A27) OBDa (96-98 Civic)

Best damn explanation.


On USDM G2s there is a "Radiator Fan Control Module" (RFCM = Radiator Fan Control, FANC A20 OBD2a pin-out) it turns on the radiator fan when A/C is on and/or if engine oil temp is too high, the "Engine Oil Temperature Switch" can turn the radiator fan on, [through the RFCM] even when ignition is off.

With that said, the "Engine Coolant Temperature Switch" (ECTS) will trigger the "Radiator Fan Relay" (RFR) any time the coolant overheats, [about 194 degrees F].

http://www.honda-tech.com/showthread.php?t=2757123

If radiator fan is not turning on...

Test for power at the fan, [white to blue/black on fan] fuse 12 - 15A, [hot at all times].
Test for power at Radiator Fan Relay. [yellow/black to black/yellow at relay] fuse 21 - 15A, [hot in run].
Test for ground at relay, [black].
Use a jumper to supply a ground to the blue lead at Relay, [ground for fan] does fan turn on?
Use the jumper to supply a ground to the yellow/green lead at relay, [from ECTS] does fan turn on?

The 94-98 Integra’s do not have the RFCM (=Radiator Fan Control, FANC A20 OBD2a pin-out) and the ground is constant at the radiator fan, the 12V is switched by the RFR and radiator fan operation is controlled by the ECU/ECM when A/C is on, but again it is controlled directly by the ECTS, [through RFR] when engine coolant temperature reaches 196-203 degrees F.

The tests are about the same...

Check for a constant ground at the rad fan, [black].
Test for 12V at the relay 94-97 is fuse 33 - 20A, [hot at all times] sorry color is not available and the black/yellow lead at relay fuse 13 - 7.5A, [hot in run].
Use a jumper to supply 12V to the fan lead, [black/red] at the relay, does fan turn on?
Use a jumper to supply a ground, [ign. must be on] to the ECTS lead at the relay, [green], does fan turn on?
A 98 is a little harder as relay is in engine bay fuse box, but test for ground at the rad fan, [black].
Test for power at the relay, [pull relay] there should be two 12V terminals, one of the bigger ones fuse 57 - 20A, [hot at all times] a smaller terminal will also be 12V, fuse 17 - 7.5A, [hot in run].
Use a jumper to connect the two bigger terminals in the relay socket, does fan turn on?. 94