Fan working but never kicks in when running or with AC on

Sep 28, 2020
9
1
Hi everyone,

First time posting here so grateful for any responses.

I have noticed that my radiator fan on my car isnt kicking in at all. So far I powered it directly from the battery and it does work. But bridging two of the three pins on the radiator temperature sensor does not start. I am having the thermostat/housing/sensor replaced as part of a coolant leak I discoverd but can't think why the fan wouldn't kick in either for the AC? I have also never seen an overheating warning light come on. I have also checked all appropriate fan/climate control fuses.

Any advice on what to check for next is would be great.

Cheers

The car is a Seat Ibiza 1.6 Petrol 2008 105bhp
 

RUM4MO

Active Member
Jun 4, 2008
6,323
469
South Scotland
There will be a fan controller in there, and either it or its wiring is faulty, have you checked both fan speeds by applying a short into the thermal sensor plug? It would be better to check that both speeds are still working as I'd think that your fan will have 3 wires going to it, one is earth, one is 12V direct to fan motor and the third is 12V to a dropper resistor, typically this resistor burns out so you only end up with the fast fan speed, also maybe these 2 speeds have 2 fuses, so check both of them in case one of them covers the operation of the fan controller - I can't be sure about that. Trust Google and the interwebnet as much will have been written on this topic typically under "VW Golf cooling fan not working" or a phrase similar to that and the same system is used or has been used for many years.
 
Sep 28, 2020
9
1
There will be a fan controller in there, and either it or its wiring is faulty, have you checked both fan speeds by applying a short into the thermal sensor plug? It would be better to check that both speeds are still working as I'd think that your fan will have 3 wires going to it, one is earth, one is 12V direct to fan motor and the third is 12V to a dropper resistor, typically this resistor burns out so you only end up with the fast fan speed, also maybe these 2 speeds have 2 fuses, so check both of them in case one of them covers the operation of the fan controller - I can't be sure about that. Trust Google and the interwebnet as much will have been written on this topic typically under "VW Golf cooling fan not working" or a phrase similar to that and the same system is used or has been used for many years.

Hi, I have shorted the thermal sensor plug and the fan does not start at all regardless of which pins I try. i have also checked and replaced the fuses under the steering wheel. I have also replaced the radiator fan control unit. The fan itself works like I said so I cant think of why it still doesnt seem to be starting. Ill google around and see what I find. Thank for your help :)
 

RUM4MO

Active Member
Jun 4, 2008
6,323
469
South Scotland
Small fuse maybe under the bonnet, I'm not sure if these cars had that extra small fuse box there - certainly earlier ones did, and that small fuse is probably badly described in the handbook - if the handbook even includes it. Your car is an early MK5 so should have a small fuse box at the side of the battery.

Edit:- there should be space for 6 fuses in that small fuse box, fuse 2(30Amp) and fuse 3 (5Amp) should get checked.

Another Edit:- main fusebox fuse 2 (mini 10Amp) and fuse 38 (ATO 30Amp) also.
 
Last edited:
Sep 28, 2020
9
1
All the fuses underneath the bonnet are fine. For the fuses underneath the wheel, probably a stupid question but should I be looking for a fuse diagram for a 2008 or 2009 just so I know the correct locations/other fuses to check.
 

RUM4MO

Active Member
Jun 4, 2008
6,323
469
South Scotland
Bother, are you implying that SEAT changed the wiring of this car between launch and 2009, or are you thinking that 2008 will mean the previous model of Ibiza ie MK4 and 2009 will cover your version of Ibiza ie MK5. From memory, MK5 Ibiza fuse box is mounted the correct/logical way up, the same age Polo has the fuse box mounted upside down - what was VW thinking about!
 
Sep 28, 2020
9
1
well I used the information off This website and as you can see the fuses for 2008 and 2009 so different things so that is what is confusing me. Also there diagrams are the other way round, the little square is on the left in my car.
 
Sep 28, 2020
9
1
Hi,
I posted in this forum a couple weeks ago trying to solve my radiator fan issue.
Basically, the radiator fan is not kicking in when the car is hot/even when the overheating light comes on. I have tested the fan directly with 12v- it works. I’ve bridged the pins that are attached to the radiator temperature sensor - it works on high and low.
I have also recently replaced:
Water pump
Thermostat & housing
Radiator
Radiator fan relay/control unit
Radiator temperature sensor
And fuses seem fine

but after all this, the fan still doesn’t kick in.
Has anyone got any ideas at all? What to try next?

Car: Seat Ibiza 1.6 2009 Petrol 105 Bhp
 

RUM4MO

Active Member
Jun 4, 2008
6,323
469
South Scotland
You should really have added this post to your original thread to keep things all together.

Anyway, you have proved that the cable and fan control unit works by bridging the correct pins for Hi and Lo speeds work and switch the fan on in both Hi and Lo speed, so replacing that radiator thermal sensor assembly should have fixed this if the water at that point is reaching the correct temperature or higher, so maybe you need to find out what the temperature is at that point in the radiator by using an IR thermometer, ie a "point and read" one.
 
Sep 28, 2020
9
1
You should really have added this post to your original thread to keep things all together.

Anyway, you have proved that the cable and fan control unit works by bridging the correct pins for Hi and Lo speeds work and switch the fan on in both Hi and Lo speed, so replacing that radiator thermal sensor assembly should have fixed this if the water at that point is reaching the correct temperature or higher, so maybe you need to find out what the temperature is at that point in the radiator by using an IR thermometer, ie a "point and read" one.
Whoops my mistake, new to posting on forums and I imagine it’s too late to move it now.

What sort of temperature should I be looking at or does it depend based on the radiator sensor I have ?

just seems odd to me that it wouldn’t even turn on if it shows then overheating symbol on the dash.
Thanks for the reply, appreciate your help :)
 

RUM4MO

Active Member
Jun 4, 2008
6,323
469
South Scotland
I was assuming that you have bought the correct and genuine VW Group thermal sensor that screws into the radiator - is this what you have done?

At a guess, the coolant temperature would need to be close to 100C before the fan slow speed would switch on Lo speed and 110C for it to change to Hi speed.

Have you checked all the areas you can reach to make sure that the engine coolant is getting circulated and is getting hot - is the cabin heater giving out hot air when that is selected?
 
Sep 28, 2020
9
1
I was assuming that you have bought the correct and genuine VW Group thermal sensor that screws into the radiator - is this what you have done?

At a guess, the coolant temperature would need to be close to 100C before the fan slow speed would switch on Lo speed and 110C for it to change to Hi speed.

Have you checked all the areas you can reach to make sure that the engine coolant is getting circulated and is getting hot - is the cabin heater giving out hot air when that is selected?
the radiator sensor is just one from my local garage, the brand is “cambiare”?

perhaps me running it for 10-15/20 mins has not got it hot enough?

The cabin temperature gets nice and toasty and the top radiator pipe is warm and bottom is a lot cooler too. Did originally have a huge airlock but managed sort that out and the coolant level is staying where it should.
 
Sep 28, 2020
9
1
It’s alive!!!
Turns out we hadn’t run it hot enough after replacing the sensor/radiator and the colder afternoons and nights had done enough to keep the engine cool without the fan having to kick in.

Thank you for your help RUM4MO
 
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