so ive been trying to troubleshoot my 91 civic hatch cuz the radiator fan comes on as soon as i turn the ign on. i didnt really mind it when i first put the swap in (obd1 d15b) but now i wanna get the last bug out of it since i already passed smog an fixed everything else. also ive noticed it has a cold driving issue like its being held back and really hesitive an not responsive. im guessing the ecu thinks the motor is already at operating temp all the time hense the fan being on constantly.

things ive tryed:

unpluging the ect sensor-still on(shouldnt it turn off?)

one of the wires on the ect connector gets 5v w the ign on and the other wire is grounded with the ign off but not grounded with ign on??

testing the ect-seems fine the resistance rises as the temp drops vise versa

testing relay- also seems to be working. with 12v applied ther is continuity between the other two wires(on the relay). and no continuity with no power... also the relay comes on as soon as the ign is turned on

keep in mind when i bought the car w no motor i opened up the eng harness just to make shur everything looked ok an everything looked oem except a random yellow wire was running to a black wire that was just twisted together witch went to ground 101 on the thermostat. i traced it back the other way an it went to a pin on the ecu that said connect to ground with another pin#. so i just left it. so the only thing i cld think of is the ect circuit is grounded befor it reaches the ect sensor therfor tricking the ecu into thinking the engine is at 190deg all the time.

any comments or suggestions would be awsome as im going to be stressen on this damn fan until it works properly. also if someone knows exactly how the ect circuit operates feel free the explain it to me so i can fully understand.

thanks casey

 

bump

 

Try this, on the back of the block there is a cooling fan switch screwed into the coolant passage,( yel/grn Wire to it and black ) it controls when the Cooling fan comes on ( around 90c ) The relay for the cooling fan is behind and around the passenger headlight. Bracket bolted to the right fender I believe... Unplug the switch if the fan shuts off there its probably a bad switch.( grounded all the time) If it stays on its a good chance the relay has stuck closed, thats why it runs all the time when the key is turned on since the relay power comes from the ign side of the car.

The ECT sensor circut is seperate from the cooling fan circut and is only used for the ECM to know what the engine temp is. It has NO control over the turning off or on of the cooling fan.

 

Ditto the above^^^
ECTS = engine coolant temperature sensor, to ECU/ECM and temperature gauge.
ECTS = engine coolant temperature switch, to rad fan relays coil. 94