My Skoda Octavia vRS 2007 fan has been constantly on. If you turn the car on, after about 10 seconds the fans will kick in and will not stop until the car is turned off. The fans also turn off as soon as the car is turned off. For some reason or the other I think it started when I went to get the air conditioning recharged although that didn't work, probably due to something else. Seems to me that may have caused this fan to be on. Just  as a side note it isn't the DPF regen.

hi-fin, I have faced this problem earlier, this is not a common issue it indicates that ur baby is not controlling heat while running so, there is an issue with a cooling system please do cross check with your cars cooling system if all of them was working well then there is an indication that u need to replace ur fan because there wer several reasons for this (in general malfunction of fan ic  due to this after turning off ur engine fan may run for a while approx in 30 to 50 sec ) not sure about this but it happend to me after replacing my fan I have rectified with this problem.

I don't think that's the problem as the fan doesn't run after turning off the engine.

If it is the smaller fan coming on, I believe that starts when the air-con is switched on.

Turn off the air-con and see if the fan is off too.

I'm pretty sure it's the bigger one, when the air-con is off the fan does not stop. Im going to check the temperature sensors just incase they are faulty.

Edited 18 June, 20187 yr by Fin_

if it was a big one then it's 100% sure that its a radiator fan(engine cooling)-actually when u turn on ur engine obviously ur fan turns on, i think ur fans bearing were worn out and it is making a quite loud sound recently so ur noticing it now, its not an issue plz take a trial run of 10km in early morning. if ur noticing any sever heat, then please check following steps 1. check with coolant level. 2 is there any particle stuck in and around of radiator r it's pipe(clogged radiator fails to cool ur system) this runs fan for no reason, if everything is fine then there are no issues. finally, u need to check fuse PLACED ON ABOVE BATTERY fuse no 3,6(30,40amperes). 

Just found out it is both the fans (air con and engine cooling). When you unplug the fuse for the air-con it completely stops both the fans instantly.

Edited 20 June, 20187 yr by Fin_