geekdude

ok so I am still troubleshooting my 93 civic that overheats. I fixed a problem with the vtec oil pressure solenoid if that makes any diffrence. I was told to check the engine coolant temperature sensor because my radiator fan would not turn on. The sensor reads the propper resistance for the temperature. when jumpered with a resistor to make the car believe it is allready hot the car just starts rough. From the schematic in my pdf of the manual (snippet enclosed) the only way the coolant temperature sensor could make a difference is if the ecu and the coolant temperature switch (diffrent than the sensor) both control the fan. I would just like verification that this is how it works since I kind of feel like i'm chasing ghosts here. also at what temperature, or point on the temperature gauge does a normal EG civic radiator fan come on? I cant seem to find this info in the manual


tldr: does the ecu play a part in controlling the radiator fan, and at what temperature is my radiator fan supposed to come on?

baller status

There are three coolant temp "sensors". One for the ECU, one for the gauge, and one for the fan.
Two months ago I could tell you which was which.
ECU enrichens the fuel mixture maybe.
Fan comes on around 203f if I remember correctly. Check the Helms.

geekdude

ok that makes since. The coolant temperature switch is susposed to start switching on at about 207. I dont know how to check the temperature of the coolant when its hot because its allways closed. Externaly I have never seen it get above 190 something on a hot day but I can imagine the coolant is much hotter than the outside of the block. do you know what point on the temperature gauge corresponds to that temperature?

geekdude

nevermind I think I found the answer

geekdude

I actualy witnessed the cooling fan turn on! I have now verified that the cooling fan and temperature sender unit works. The temperatures listed do not varry much form the temperature of the exterior of engine. im guessing there is not much thermal barrier in the metal of the engine block. I have noted an issue with the fan shroud that i should have fixed when i replaced the radiator. i will fix that and take it on a road test to see if the issue is still there.