# T30 X-trail engine cooling fans not starting - overheating



## alejoc (Dec 18, 2019)

Hi everyone.

Last week I had an overheating problem with my Exy (QR25DE 2008 T30 auto trans), the temperature rose suddenly in traffic and coolant started to boil. Had to stop in traffic and have the car towed to my mechanic. Both cooling fans would not start even with AC on and engine temperature over 90°C.

The wiring was thoroughly checked, as well as the fan motors, which work when plugged in directly to the battery. The relays were also tested and operate. The mechanic suspects that the ECU is not sending the signal to turn the fans on. Has anyone else had such a problem?


----------



## otomodo (May 23, 2008)

Unless the ecu is programmed differently in warmer regions in the world, 90c was normal temperature operation, if my memory serves me well. 
Was it boiling at 90c when the mechanic checked it?
Is your ac blowing cold air?



Sent from my SM-G781W using Tapatalk


----------



## alejoc (Dec 18, 2019)

otomodo said:


> Unless the ecu is programmed differently in warmer regions in the world, 90c was normal temperature operation, if my memory serves me well.
> Was it boiling at 90c when the mechanic checked it?
> Is your ac blowing cold air?
> 
> ...


It reached more than 100 and started to boil when I had to stop the car, I have seen 90°C usually in traffic with my OBD app, but the thing is that even when it overheated, the fans did not start, so they suspect either the relays are faulty or there is some problem with the ECU control signal. Thermostats and temp sensor were changed with original ones already. The AC stopped working when I had the overheating event, and when they checked the car no fan turned on with AC active.


----------



## alejoc (Dec 18, 2019)

Situation update. Found a great electrical auto repairman who found out that the signal from the ECU was not being detected by the fan relay, so it seems that the wire that conducts that signal is somehow damaged. He installed a bypass and now I am a happy Exy motorist again. I suppose that spending a few years in coastal regions near the beach took its toll.


----------

