My R reg ST2 has the degF gauge. Have seen 230deg and the fan not run. Believe it should have runat this temp. Am i correct. Have checked the fan motor and its OK. Have tried removal and linking the sensor in water pipe and this must run gauge. Am raedy to cut the wires and put a toggle switch to it. But before i do... Where is the relay to it shown on the diagram. I have found 5.... 2 under seat, believed not for it as they are changover type. too many terminals. what about the 3 at the front? The wiring diagam colours dont seem to match anything. Can we identify function of all these relays.
The fan should come on before 220F. There are 2 temperature sensors; the one on the horizontal cylinder is for the LCD readout, the one on the vertical cylinder goes to the ECU. The ECU uses this sensor to adjust the fueling according to coolant temperature and to switch on the fan via the relay when the temperature exceeds a preset limit. Of the 2 relays under the seat, one is for the fuel pump and coils, the other is the fan relay and they are interchangeable. I can't remember which is in which position but the wires to the fan relay are violet/black, violet/white, yellow/black and grey/black. To test the relay swap the two of them. If the fuel pump doesn't run at switch on then the relay is faulty. I have had problems with my ST4s though, where the fan wasn't switching on. Testing showed the fan was ok and the relay was ok but the ECU wasn't switching it on.
Thank Derek. Helpful. I have bench tested the relays under the seat and they are OK. So its either the sensor or ECU. Will try and test sensor but. I feel plan B coming on. The toggle switch. Regards and thanks.
I doubt if it's the sensor or the engine would be running too rich. If you connect a switch to pin 85 of the relay ( the grey/black wire) to connect it to ground, the relay will switch and turn on the fan.
