The following instructions help you modify your 91-93 3S to let the Plag and Play Flash Ecu control your radiator fan. Take the wire coming from each of the existing 91-93 oem fan relays, that would go to their corresponding thermo switches, and wire them into the Plug and Play Flash Ecu instead.
The ecu will now act as the activation ground for the relay instead of the thermo switch.The pins on the 91-93 Plug and Play Flash Ecu are 52 radiator fan High, and 53 radiator fan Low.
The pins on the 98/99 VR4 Flash Ecu plugs are 17 radiator fan High, 18 radiator fan Low.
Find plug A-55 pin 3 (blue with black stripe). The wire coming from the fuse box instead of going into the radiator plug will be cut and go into pin 53 on the 91-93 PNP Flash Ecu. Or pin 18 on a 98-99 Flash Vr4 clone Ecu. You will have to add a length of wire to extend it and then route it through the firewall to the ecu. The ecu comes with extra pins.
Find plug A-55 pin 6 (green with black stripe). The wire coming from the fuse box instead of going into the radiator plug will be cut and go into pin 52 on the 91-93 PNP Flash Ecu. Or pin 17 on a 98-99 Flash Vr4 clone Ecu. You will have to add a length of wire to extend it and then route it through the firewall to the ecu. The ecu comes with extra pins.
Make sure pin 1(black) and 4(blue with yellow stripe) are still plugged in on A-55, only pin 3 and 6 should be re-routed. With the car on but not running you can test the relays by grounding the wire you cut. Do it one at a time. When grounded the relay will activate and turn on the fan.
When completely finished with the modification there is an easy way to test it. With the car on but not running you can test your handy work by connecting your laptop to the ecu via EvoScan. In the lower right of the screen the Actuators button can be pressed and it will show a list of fuctions you can test. You will see buttons to test both rad fan high and rad fan low. Sometimes you have to connect to the ecu and then stop datalogging before the actuators work.
The 91-93 PNP Flash Ecu comes with extra pins and plug.If you do the modification this way you don’t even have to remove the two thermo switches. They are electrically removed from the circuit and won’t affect anything. Plus if you want to go back to stock it will be an easy retrofit.