Hi guys I have a 97 civic hx that is overheating but I changed the thermostat and the fan sensor/switch and I ran power to the fan to c if the motor is good an it is and to the relay which is working also. But basically the fan is not coming on at all ?? Any ideas any help would b greatly appreciated!!!!

 

Wait, you supplied 12V to the fan motor and it turned on, correct? Did you check to see if there is 12V at the fan when the coolant temp is up over 200F? That would tell you if the new temp sensor is good.

 

If you have no flow:
* Lack of coolant / didn't purge air / gas from bad head gasket
* Thermostat stuck closed
* Clogged radiator
* Water pump impeller fell apart (extremely rare unless plain water has been used for an extended time)

the lower hose will never get hot enough to actuate the sensor and turn on the fan. Meanwhile the engine will overheat.

Does the heater work? That generally shows there is sufficient coolant and the pump works.

 

Wow u guys are amazing I didnt expect that many response so fast !! So no I haven't tried shopping power to fan when heat is up over 200 so I'll have to try that and also I didn't purge air from system I just refilled it after working on it. Also my car runs at high rpm right now when I start it it's at like 1500 and cruises at 3000 ! My heater does work. I am off tomm so will hopefully try these ideas you guys gave me! Thanks a million!!

 

Geez guys sorry took so long for reply , finally had whole day to work on car. It was the RELAY, I'm an idiot . I decided to just replace it even though tested it an the fan kicked on w In 30 sec! Thanks for all comments!!!