Octavia radiator fan on from cold

[Skunkworks11]

Hi everyone

 

Car is Octavia 1.9dti mk2 2010.

 

Fault started about 3 weeks ago and has steadily got worse. Fan would come on and off randomly during journey whether engine was hot or cold.

 

it now comes on within 5mins of starting and runs the whole time, only stopping when i turn ignition off and you cam hear fan slowing down.

 

From reading other post i believe there is 2 temp sensors( 1 engine water temp and 1 on radiator) and a fan controller

 

My question is, which one is most likely to be at fault with the symptoms I'm getting ?

 

Thanks in advance

 

 

[Westbury63]

On the two occasions when the engine temp sensor on my MK1 Octavia failed, it was apparent by the temperature guage not working correctly. If your temp guage is reading normaly, then that would suggest to me that it would be the sensor on the radiator you referenced.  Hope that helps.

[Skunkworks11]

Thanks Westbury63

 

Yes, i believe temp gauge is showing correct temperature as it climbs up to 90 .

 

I will start with radiator sensor and see how it goes from there.

 

Don't suppose anyone knows the Manufacturer of the Genuine sensor?

 

 

[Westbury63]

Pleased to help. 👍

 

I find this a very useful resource: https://skoda.7zap.com/en/cz/octavia/oct/

You can find the part number you need and then google to find the best part/price etc. Still worth checking it matches the part no on the car however just to be sure.

 

 

[Skunkworks11]

Excellent Westbury63, thanks....i will check it out 👍 

[KenONeill]

@Skunkworks11 - That sounds like pretty normal behaviour when the aircon is on.

[Skunkworks11]

@KenONeill interesting although AC switch/light is not on when I'm getting the symptoms.

 

It started of with the fan coming on randomly and idle revs of 1000 no matter the temperature of the engine, it has steadily got worse over last few weeks and now runs constantly although takes a few mins after starting  for fan to kick in.

 

When i turn car off i here fan slowing down, restart car and few mins later fan back on.

 

Temp gauge in car climbs up to and sits at 90, so as Wesbury63 posted earlier should rule out the engine temp sensor.

 

Open to suggestions, just looking for the most likely culprit as a starting point....

 

Should also have noted i checked for error codes, of which there is none

[KenONeill]

@Skunkworks11 - I've got an idea maybe. Has there been any change in the fuel consumption?

[Skunkworks11]

Don't believe there has been any great change in fuel consumption, obviously if revs go up due to fan coming on then it has to use a bit more diesel

[Skunkworks11]

Just a quick update, just been out in car, from cold i drove about 2 miles and temp gauge started going up.....got about 3 notches up from start position so something around 65c and fan came on

[KenONeill]

@Skunkworks11 - Sorry, seems pretty normal operation for a/c on to me.

[Skunkworks11]

@KenONeill no need to be sorry, who knows, maybe something else in the AC system is to blame..as i don't have any error codes i can only guess at what the fault is and the reason why i posted on the forum.

 

Someone i spoke with thought it might be DPF regeneration but I don't have one so it can't be that...lol

 

Hopefully getting radiator switch changed on Monday so hopefully that cures it, if not its back to the drawing board.

 

 

[silverback1972]

I had the same symptom ( not saying it's the same fault) with my MK 2 Octavia. The fan would come on within 5 mins of starting  and revs would go up, fuel economy went South. It turned out to be a dodgy DPF sensor. Even though the DPF light didn't come on the car kept going into regen mode. Sensor changed and it fixed the issue. 

[Skunkworks11]

@silverback1972 thanks, that was the inital thoughts as the idle revs go up to 1000 when fan comes on but don't know if mine has a DPF ...

 

Getting radiator switch changed tomorrow to see if that cures it but maybe i should find out if i do actually have a DPF as that does sound like a good call....cant say ive noticed a change in fuel consumption though

[Anddenton]

21 minutes ago, Skunkworks11 said:

@silverback1972 

Getting radiator switch changed tomorrow to see if that cures it but maybe i should find out if i do actually have a DPF as that does sound like a good call....cant say ive noticed a change in fuel consumption though

No UK 1.9's had a DPF

[Skunkworks11]

@Anddenton 😭...lol well that rules that out. Hopefully radiator switch sorts it tomorrow !!

[Skunkworks11]

Update on radiator switch....its now been changed for almost a week and it's made no difference.

 

Fan just does its own thing....engine coolant cold or hot, fan just does its own thing and comes on when it feels like it.

 

Back to the drawing board ☹ 

[Mikek3111]

I had a very similar issue with my old mk2. It had new fans new sensors, new ambient temp sensor even a new fuse box and none of these cured it. Best to get a scan done of the vehicle first before randomly changing parts as trust me it gets expensive. Mine turned out to be water in the ecu. Hopefully yours isn’t but you should be able to find my old thread here and there is a lot of useful info in it both from myself and others and well as info I got from spending hours with a Skoda master tech going through wiring diagrams etc

[Skunkworks11]

Thanks Mikek3111 , will try and track down your post  and give it a read...

 

Haven't resorted to help from a garage yet but ive checked for error codes and nothing present.

 

[Skunkworks11]

Just read your recommend post, you didn't half have some trouble tracking down the fault.

Atleast you have EML light coming on and fault codes....im getting nothing except fan coming on as and when it pleases.

The thing I find strange is, if i turn ignition off when fan is on i hear the fan slow down....start the engine again and all's fine for a short while then it comes on again. I would have thought if the car thinks the engine needs cooling it would come on straight away 

[Westbury63]

Sorry to hear of the ongoing saga.......cars can be a pain in a**e!

 

I wouldn't usually suggest parts darts, but given the price of the engine temp sensor and how easy they are to fit, I think I would be tempted to try one. If nothing else for the purposes of elimination and being such a cheap and simple item to change.

[Skunkworks11]

Hi Westbury63,

Yes they definitely can be and this one is...lol

Agreed, for the price of the temp sensor it probably worth a go although temp reading on dash looks to be fine. Might try and get the actual output from ECU and see if it matches what's displayed on dash.....failing that just go for sensor change and see.

 

Am i right in thinking said sensor is to the right of the engine under engine cover ?

 

[pikpilot]

On the Mk1, and could be the same on the Mk2 1.9, the temp sensor is a dual unit with one output used for the temp display and a second output used by the ECU for engine functions. So a failed sensor will often have the correct temperature display.

[Mikek3111]

13 hours ago, Skunkworks11 said:

Just read your recommend post, you didn't half have some trouble tracking down the fault.

Atleast you have EML light coming on and fault codes....im getting nothing except fan coming on as and when it pleases.

The thing I find strange is, if i turn ignition off when fan is on i hear the fan slow down....start the engine again and all's fine for a short while then it comes on again. I would have thought if the car thinks the engine needs cooling it would come on straight away 

Yeah mine used to stay on even when the car was off and keep going till it killed the battery. In the wiring diagrams Skoda show 2 temp sensors. 

While I think of it does your ambient temp reading (outside temp) inside the car work? That can also trigger the fans

[Skunkworks11]

Thanks pikpilot.

Is this the engine sensor you are speaking of ? I haven't looked/found engine sensor yet, I have changed the sensor on the bottom of the radiator and that was just 2 wires.

 

I will defo look into it and get it changed either way and take it from there.