coolant temperature and fan problem please help

[Redace]

No because there is a sensor in the radiator that controls the fans.

Thanks for that, was just a bit worried as it has kept at 60 today and ive done about 30miles and its not moved and i never heard the fan kicking in!!

Im bloody useless with cars, just not my thing normally but with the credit crunch ive had to downgrade from a Freelander to a Seat (if im honest im loving the Leon, forgot what it was like to pull off fast lol) and having to learn to do things for myself instead of going to the garage

 

[Redace]

This was in the manual, thats why I thought it might not have kicked in

'The radiator fan is driven electrically and
controlled by a thermoswitch from the
coolant temperature (also from the
engine compartment temperature on
some models).'

 

[Muttley]

The coolant temperature sensor unit has two separate sensors in it, one driving the dash gauge and another going to the ECU. So the dash gauge can be out and the ECU still getting good data.

The cooling fans are worked by a completely separate thermoswitch that is mounted in the radiator itself. No connection to any other engine electronics. It only works according to the temperature of the water in the radiator itself.

The only exception is if you have air conditioning. In this case there is an additional fan control module which turns the fans on at the lower of their two speed settings as soon as the air conditioning compressor is turned on. This is to draw air over the condenser, fitted in front of the radiator, so that the cooling system works.

 

[Redace]

Thats great news, as i said ive bought one but dont know when i'll have time to fit it prolly take me 3 hours lol.

So i presume its safe to drive as normal then?

Thanks all for the help ... you have a cracking forum here !

 

[Muttley]

That's a very big question.

Your dash gauge has stopped reading, so you have no indication of your engine coolant temperature. This means any one of a number of things may go wrong and you won't know about it.

You need to find out why the dash gauge isn't working. The CTS (Coolant Temperature Sensor) is the prime suspect, but it isn't a certainty.

There are some checks you can make. If you have aircon i.e. you have an air cooling system as part of the cabin air system, then when you press the "snowflake" button (turning the air cooling on) the fans should begin to run at the slower speed (this is still quite fast). This will tell you that the fans are at least able to suck air in, they haven't failed.

Next, go for a 15-20 minute, reasonably vigorous run, then open the bonnet and see of the fans are turning. This will tell you if the thermoswitch is working and the fans are being activated by the water getting hot.

You should be cautious until you've got the dash gauge working again.

 

[Redace]

Coolant

Thanks muttley,

Well I can hear the fans from inside when I turn the aircon on when looking in the engine one of the fans goes round when the aircons on but the one on the battery side stays still.

I'll take it for a good run and report back

Thanks

 

[Redace]

OK ... Took it for a good run, about 40 mins pulled up every 10 mins to see if I can see the fan moving but nothing every time, so i ran it stationary and the fan came on the one that's in line with the steering wheel, which was the same one that came on when I turned the aircon on. The other fan doesn't seem to move at all !! ... should it ? or is it just an auxiliary fan in case it gets really hot ?

 

[Muttley]

Both fans should come on together. If one fan isn't moving then it needs to be checked, either the wiring is faulty or disconnected or the fan is duff.

From your description it's the big fan that's not moving. You need to find out what's wrong straight away, the big fan is the main air mover.

 

[Redace]

Both fans should come on together. If one fan isn't moving then it needs to be checked, either the wiring is faulty or disconnected or the fan is duff.

From your description it's the big fan that's not moving. You need to find out what's wrong straight away, the big fan is the main air mover.

Ahh poop .... Whats the best way for me to check it myself or is it a case of going to a garage?

Thanks

 

[Muttley]

Depends how comfortable you are with auto electrics.

I'd start by disconnecting the fan and applying 12V from the battery to each of the connections. I'd connect a flylead to the fan connector and use the free end on the battery - there will be sparks and you don't want to damage the connector. That will tell you if the fan is dead or if it's something else. If the fan is ok then it is most likely to be the fan control module.

However, there is one thing you could do before all that. Two of the fuses on top of the battery are for the radiator fans: the middle one of the five metal strip fuses, and one of the green 30A blade fuses. Check that they are not blown and that the connections are good and clean, especially for the big metal strip - it's got a nut and spring washer at each end, check the contact areas underneath the fuse itself to make sure it has good clean connections.

 

[Redace]

Depends how comfortable you are with auto electrics.

I'd start by disconnecting the fan and applying 12V from the battery to each of the connections. I'd connect a flylead to the fan connector and use the free end on the battery - there will be sparks and you don't want to damage the connector. That will tell you if the fan is dead or if it's something else. If the fan is ok then it is most likely to be the fan control module.

However, there is one thing you could do before all that. Two of the fuses on top of the battery are for the radiator fans: the middle one of the five metal strip fuses, and one of the green 30A blade fuses. Check that they are not blown and that the connections are good and clean, especially for the big metal strip - it's got a nut and spring washer at each end, check the contact areas underneath the fuse itself to make sure it has good clean connections.

Great I'll have a good look today, is it risky to drive on a longish drive, need to go to a freinds about 70 miles away at the weekend

 

[Muttley]

I have to say that I would be nervous driving the car at all in this state. Known fan failure plus dash temperature gauge malfunction - you could boil the engine dry and the first you'd know is steam coming up from the bonnet.

It may be all right as long as you can keep it moving (within reason - not so fast as to stress the engine), but if you get stuck in traffic you risk overheating.

If you do decide to take the risk, leave the aircon off (to stop the aircon condenser dumping heat into the engine coolant radiator) and set your cabin heater to full hot, max fan. The cabin heater matrix will act as a secondary radiator, with the cabin ventilation fan will help a bit.

 

[Redace]

I have to say that I would be nervous driving the car at all in this state. Known fan failure plus dash temperature gauge malfunction - you could boil the engine dry and the first you'd know is steam coming up from the bonnet.

It may be all right as long as you can keep it moving (within reason - not so fast as to stress the engine), but if you get stuck in traffic you risk overheating.

If you do decide to take the risk, leave the aircon off (to stop the aircon condenser dumping heat into the engine coolant radiator) and set your cabin heater to full hot, max fan. The cabin heater matrix will act as a secondary radiator, with the cabin ventilation fan will help a bit.

Thanks for all your info Muttley its very much appreciated!!

I looked at the fuses today all seems fine, I spoke to a bloke at kwik fit (got a tyre quote) and he says that the fact the smaller of the fans comes on at temp it should be enough to cool the engine (took with a pinch of salt)

One thing I have been thinking is .... I take it the big fan is the engine fan and the smaller is the AC fan, if this is right then why does the smaller of the fans come on to cool the engine when its sitting still, does that mean someone has changed the wiring as the big fan is broke? or does the smaller fan come on anyway?



Im putting in the new sensor tomorrow so lets hope it does the job as far as the gauge is concerned.

 

[Muttley]

It is incorrect to think of the fans as having separate functions. They are wired in parallel to come on together. In the 1.4 engined cars, the second, smaller fan is only fitted to cars with air conditioning (as far as I can tell). However it is there to provide additional airflow across both radiators (since they are in parallel) and is expected to come on together with the bigger fan.

The same is true of all Mk.4 Golf-derived cars with two radiator fans. Both are meant to come on together.

 

[Redace]

It is incorrect to think of the fans as having separate functions. They are wired in parallel to come on together. In the 1.4 engined cars, the second, smaller fan is only fitted to cars with air conditioning (as far as I can tell). However it is there to provide additional airflow across both radiators (since they are in parallel) and is expected to come on together with the bigger fan.

The same is true of all Mk.4 Golf-derived cars with two radiator fans. Both are meant to come on together.

Ok ... I have fitted the new sensor and alls good so at least i will know if it starts over heating, I have also checked the fuses and they all seem fine, so it must either be a resistor, the control or the fan itself.

Does anyone know which cars will have the same fan so I can try to get a fan/resistor/control unit from ebay ?

Thanks again Muttley

 

[Muttley]

You really need to check the faulty fan to see if it just the slower speed that has failed. If so, then you could replace the failed resistor with an external one mounted on a bit of aluminium as a heat sink.

http://website.lineone.net/~alan.james.lorely/fan mod/Repair.html

Or you could get a Nime box and fit that to provide an alternative and better fan speed control.

http://www.nime.co.uk/content.php?mk4fans

The fan failure has been discussed to death on the UK MkIV's forum

http://uk-mkivs.net/forums/p/59897/488123.aspx
http://uk-mkivs.net/forums/p/2088/17772.aspx#17772

Replacing the fans is very expensive (more than £100 each, I think?) and it is possible they will fail again with the same problem. Replacing the fan control module with an updated one is supposed to fix this, but adds more expense.

 

[Redace]

You really need to check the faulty fan to see if it just the slower speed that has failed. If so, then you could replace the failed resistor with an external one mounted on a bit of aluminium as a heat sink.

http://website.lineone.net/~alan.james.lorely/fan mod/Repair.html

Or you could get a Nime box and fit that to provide an alternative and better fan speed control.

http://www.nime.co.uk/content.php?mk4fans

The fan failure has been discussed to death on the UK MkIV's forum

http://uk-mkivs.net/forums/p/59897/488123.aspx
http://uk-mkivs.net/forums/p/2088/17772.aspx#17772

Replacing the fans is very expensive (more than £100 each, I think?) and it is possible they will fail again with the same problem. Replacing the fan control module with an updated one is supposed to fix this, but adds more expense.

Thanks again, I have seen this fault on google, I saw the fix but in all honesty I wouldnt have a clue where to start, these sort of things just go right over my head, would a car sparky be able to do this if I was to show them the link? Im fearful of taking it to a garage as I wouldnt know if what they are saying is the truth or if they are trying to rip me off lol


Ive had a quote of £190 for the fan and £50+vat to fit it which is a lot if its just going to go again.

So any 2 fan system from a mark IV golf with a 1.4 engine should fit then ? would other engine sizes fit or would they all be different ?

 

[gazR]

ive got a similar problem with fans not working on slow speed. i went to TPS to price them up, i dont have the exact price for the 345mm fan but im sure it was around £130+Vat so about £156.

Just found the prices from my local seat dealer:

240mm - £159.88
345mm - £166.94

and the fan control unit £117

 

[Muttley]

Redace, an auto electrician should be able to do this but it's custom work and will be charged accordingly. It's cheap as a DIY solution because you don't have to pay for the labour.

The fan connectors are held in a clip at the bottom of the radiator shroud, needing the undertray to be taken off to get access.

You really need to confirm the actual fault, first by testing the fan to see if it really is broken. Apply 12V to the fan leads directly at the connector. Negative to the brown/black lead, positive to red/white for the low speed, to red/black for high speed. Make sure nothing is near the fan blades to get caught up or cut, including your fingers.

If the fan works, check the control module, then the wiring.

But if you aren't comfortable with electrics, then an electrician is your best bet. Try to get one by recommendation if you can.

I don't know if the fans are the same across all the cars in the range. I don't have access to part numbers to check.

 

[Muttley]

gazR, those prices are the reason that the Nime box and resistor replacement options are so attractive. If it happens to me I'll be installing my own resistors.