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Hello everyone
I'm new here, currently owning a 07 civic vti
I found out the radiator fans are not working when tempeture getting high
but both of them will kick in when I turn on the AC
Did anyone know whats wrong with this ??

thanks guys!

 
Rep Power: 512

Try jumping the fan switch. If they turn on when you jump the switch, then you found the culprit.

 
Rep Power: 518

Do not jump anything if you don't know what you are doing!
If you try to jumper terminals for a 3 wire sensor plug, you can ruin the engine computer.....and that gets expensive in a hurry.

If you jumper a 2 wire temp sensor plug, the computer will just ignore that input because it is an impossible value and will set fault code(s).

If your particular car really has a temperature switch that controls the fans, that is OK to jumper as a test.
(Being as new as it is, I really think it does not use that method of fan control.)

Got fault codes?
Is the radiator completely full of antifreeze?
Got a scanner that can display live engine data on-screen? Check out ECT1 and ECT2 values when it gets hot.
Check what the ECM is trying to do with the fans, it will either be Off, low speed, or high speed--depending on coolant temps, and AC request+high side pressure reading

Check at the temp sensor in the bottom of the radiator, see if terminals in the connector have corroded or if the sensor has leaked antifreeze into the connector
(Over here in North America this sensor is the one that controls the fans, but it is a sensor not a switch, and our fans are also set up to run low speed and high speed via an extra control relay)

 
Rep Power: 512

What ezone said. Disregard my previous comment. Didn't realize it was a 3 wire sensor plug

 
Rep Power: 518

Over here the radiator temp sensor uses a 2 wire plug, but shorting it causes fault codes.


A person PM'd me the other day after applying 12v to the AC pressure sensor wires and suddenly the car won't run anymore. I believe he ruined the PCM.
Plus he still has his original problem he was trying to figure out.

 
Rep Power: 512

so.. three prong sensor wire. What is it, +12VDC, sensing line, and ground, then the PCM reads the ∆V in some overly complex algorithm?

 
Rep Power: 518

No. Most (maybe not all) variable resistor type 3 wire computer sensors (in just about any car on the road) will have a ground, 5Vref, and signal return.

Shorting the 5v line to anything can really hurt.