I just got done doing a engine swap and I started up the engine and let it warm up and the radiator fans dont come on. If the gauge on the dash shows the tempature then the senser is good right?
What else would make the radiator fans not come on ?
I made sure all wires are plugged in.

Fan Relay could be a problem or a short somewhere. Just make sure that your car does not overheat....

Yeah it overheats and blows off. The relays in the fuse box under the hood? I interchanged them and the same thing happends.. ;<[[[[br />I ran power straight to fans and they come on.. but no power from the cpu ;<[br />
Im about ready to hookup a wire to the fan and run it to the cab on a switch. will work until im drunk and forget to turn it on while im driving lol

The gauge and the ECU use two seperate sensors, though they are both in same same area of theb water neck.

______________________________
If a sentence found online has 35% misspellings or greater and includes at least two racially charged expletives, chances are it is a YouTube comment.

'95 Eclipse TurboGS (garage deco)
'95 TSi AWD (restoring a survivor)
'97 Talon ESi-T (poor impulse control)
'99 Eclipse RS-T (daily beater)
'13 Evo X (mostly stock)
'17 Sienna (Middle Aged Dad Mobile)



Factory Service Manuals: http://nawdu.de/files/

know what the sensors are called ?

When i unplug the sensor that has 3 prongs the engine changes it runs different. is there any way i can tell which sensor i need to replace?

The top sensor, just below the radiator hose neck in the thermostat housing, has TWO wires and it is the sensor that the ECU uses to determine the coolant temperature. Unplugging this could cause the idle to change since the ECU will be receiving erroneous information about the true coolant temperature. I have never seen one of these with three wires like you mention. My observations are from a 98 RS MT. Unlike the one-wire sensor mentioned below, this two-wire sensor is electically isolated from the motor block and does not depend on a ground connection through the threads of the sensor body to operate correctly.


The bottom sensor is ONLY used by the visual temperature gauge in the dash cluster. It has a single wire and needs a ground connection through the threads of the sensor body to work properly. Unplugging this sensor will only make the visual gauge quit working. It is NOT used by the ECU for any tuning purposes.

ok yeah your right its 2 wires i was drunk when i looked. I changed the one wire sensor thinking that whats the radiator fan swith . when i unplug the other sensor it idles different. But my damn radiator fans will NOT come on when i turn on the ac in the cab one fan comes on
Ive checked all fuses replaced all relays. Could the sensor when you unplug change idle but not turn the radiator fans on ? This is a pain in the ass i cant figure out wtf........

Try to use punctuation in your future replies.

I think you are saying the passenger side fan comes on when you turn on the A/C switch in the car but other than that neither turn on?

The upper sensor sends info to the ECU. If changing the upper sensor does not work and you have checked all wires, connectors and fuses then the ECU is looking suspect. I would triple check the other stuff though. Now would be a good time to get a wiring schematic and trace it all out. You can simulate the signal from the ECU to test the relays if you have to color codes to do so. The ECU simply provides a ground to any of the three relays under the hood.