[i30pylot]

Long time listener, first time caller

I have a problem with my radiator fan... It doesn't come on with increasingly hot coolant temperature, but operates normally with AC operation. Right now, if the engine heats up, I need to turn on the AC to cool it back down!

My logic engine (dodgy grey matter!) has thus far lead me to believe that the fan motor, fan wiring (post relay at least), relays (2 c/fan relays in engine bay fuse box) and cooling fan fuse are working satisfactorily as the fan starts normally with AC operation. My thinking  at the moment is that perhaps there may be an issue with the engine coolant temperature sensor or its wiring, thus the fan not getting a "start" command, but I don't know where to find the sensor to take a look or what the other symptoms of an issue with this would be.

Can anyone else shed some light on this, either along the ECT sensor line or any other potential causes?

My i30 is a 2009 1.6 CRDi manual SLX, and I love it and don't want to see it die a hot death. Help please!

[Asterix]

I think you're right about that temp sensor, but unfortunately I can't help locating it. Hopefully someone can help.

[Phil №❶]

The sensor is located in the cylinder head, just to the left of the air filter, under the big rubber cooling pipe. It has a 3 wire plug fitted to it. 1 to ground, 1 to instruments and 1 from the ECU. The function of the sensor is to change resistance in line with coolant temperature, however it works @ 5 volts in series, with a resistance derived in the ECU, as well. Unless you'e well qualified I'd see an auto electrician and have them fix / replace the faulty part.

Sensor testing requires removal from the head, immersion in coolant at various temps and measuring the resistance.

Note: If any of the 3 wires have faults, the sensor will appear to be faulty. So I would at least look for visual signs, wires touching the motor or burnt etc.

[i30pylot]

Cheers Phil and Asterix, good info there.

Phil, I appreciate your opinion re auto electrician, I do have a habit of getting in deeper than my skills would suggest that I should, all in order to save some coin where I can! Given that I will be taking it to a pro for this fix, are there any other symptoms that I should look for to confirm a dodgy ECT probe before I do? I assume that the temp would be used for a number of functions and if it is faulty there might be some other clues? I figure if I can roll up to a workshop and ask for a specific fix I would be likely to get a more accurate quote than if I just described my problem and asked them to troubleshoot and fix.

I'm also looking for a "Plan B", what else might explain this bad behaviour? Any suggestions anyone?

[Phil №❶]

I get myself into trouble occasionally too, which is why I suggest the auto electrician route for you. The sensor when working does alter the fuel timing and amount in an endeavor to lower the engine temperature, so yes, it does do more than switch on the fan.

Basically, your "fault" is going to be in these general areas

• Contiunuity, from any / all of the three wires
• A faulty sensor
• A fault in the ECU

Because it's a modern car and the wiring is quite convoluted, it won't be a simple job to test the continuity.
Pray it's not an ECU problem.