Radiator fan no longet runs !

W

will471

Radiator fan no longer runs !

I've thought for a couple of weeks that the engine wasn't cooling as it used to (well I've had the car for six months) and confirmed it on the weekend - but I cannot really see why so I'm seeking your expertise...

I went out on my weekly trip of 30 miles - and at speed so that the temperature didn't actually rise too much - and on return left it idle and saw the gauge just rise, far above what it usually get to before the fan would have started, opened the bonnet and there was simply no fan action. So far I've checked:
- temperature gauge is obviously working
- the radiator is getting hot
- the fusible link is fine (0 ohms with meter)
but in the situation as described above there are no volts across the power lead to the fan, although, as yet, I've not checked that the fan will run (it was fine a few weeks ago) but it is certainly free to rotate.

It's worrying that it almost sounds as if it's the ECU not telling the fan to start. I haven't tried the diagnostics - but I'm not sure that they would say anything interesting and the engine check light in the instrument panel just goes off as usual and stays off.

Any suggestions on what to check next ?

thanks in advance
 
you need to test the coolant temp sensor for the ecu is within spec (2pin sensor). think you can just short out the ecu coolant plug terminals to simulate 0ohm (very hot) and see if that makes the ecu turn the fan on. if not, check the fans motors working by connecting directly to the battery.
 
thanks - that's made me realise that there are two temperature sensors. So although the gauge is fine I need to check the ECU one.
Mind you they only seem about a tenner - so I suppose that they are bound to be difficult to get out, they seem to be sitting in the coolant just to make it more pleasant (well at least it's not freezing now!)
I'll do your test first, just to check
 
they not too bad to remove using a long socket compared to bolts.

yea test sensors are working before forking out money
 
I've eventually got around to looking at these - it's surprising how much cooling the cabin heater can achieve although I am a little fed up with hot ankles...
However I have been initially surprised by the fact that the upper sensor is the temperature gauge sensor (confirmed by unplugging it), and it has a single lead; the lower sensor have a twin lead. But my Haynes manual says they should be the other way around. I cannot see that it would make a lot of difference (10-15mm and they're both in the coolant, aren't they?) but can anyone confirm which way around they should be ?
Otherwise I intend to see if I can check the resistance of the faulty (almost certainly) sensor this weekend and replace it.
thanks...
 
the 2pin ecu coolant sensor is usually at the bottom and the gauge sensor is at the top but yea they're in the same stream.
 
Well, it's been a couple of months...
I did get a replacement sensor although that, in itself, took a couple of week - it seems that my K11 isn't that common, or at least that part isn't. And I installed it, and it made no difference! I did check the one I removed and it was working correctly (it was close to the specification)
As I mentioned I had checked the power to the fan and when the engine temperature was high enough to justify the fan running there was no voltage at the fuse box - re-checking and it's the same.
There had been a fuse melt in that fuse box but as far as I can tell it didn't affect the fan fuse (but...); I do have a replacement fuse box but that's not a quick installation and, at the moment, I've no garage so have to rely on the weather !
Any other suggestions ?
Could it be the ECU ?
 
No ideas, anyone ?
We've not had the best of dry spells recently but as so as there is one, the days are going to have to be spent checking all the wiring I suspect!
 
Yes, the fan motor will run. But the problem is that there is never any volts on that circuit - and I've let the engine temperature get to 40-50%. In addition there's no doubt that the engine is running rich (exhaust tail pipe not clean, and the cylinders would appear to be coking up as there is now evidence of pre-ignition if I just have too much accelerator pedal in low revs, and it certainly wasn't doing that six months ago) so, to me, that suggests that ECU just doesn't know how hot the engine is. The question is how easy is it to diagnose - hence my comment about checking the wiring because that is the next link in the chain, so to speak.
 
if you short the coolant temp sensor wires (touch em together with a clothes pin in each wire) the fan should kick in
i think the above only works with the engine running
if you unplug the fan and run positive negative to the car battery from it, it should kick in, you dont need engine running for this fan test
 
The latest is that I've done some more test and may be more confused...
I decided to check at the ECU so with the aid of the Haynes manual circuit diagram I determined which connectors went to the temperature sensor; checked it when cold and after running the engine for a few minutes - all correct !
I also saw that the manual tells of a way to check the exhaust mixture - so I ran that test and - all correct !
That would infer that there is nothing wrong with the mixture after all...
So I took out a spark plug - and while they were a little aged it was clean. Regrettably my new (*) plug socket wouldn't let go of the plug when I screwed it back in and the only way I could get the socket out was by jamming it to the extension bar with a piece of cloth. Obviously the socket set has had a bit of use (no abuse) and the locking ball was a bit loose. But as a result I decided against checking them all.
So I suspect my belief in a problem with the mixture is false and it's only the fan that's the problem; although I still have the pre-ignition and the dirty exhaust.
And then, checking the circuit diagrams I see a relay in the fan line - now it's now pouring down with rain so that's another day's job...fingers crossed that's the reason that the fan isn't running when it's told to.
I'll get new plugs (probably time) and hope that the exhaust sensor isn't lying - it's MOT time in a few months so we'll see then no doubt.
* After driving a K10 for 120,000 miles (older plug size) then a Almera for 160,000 with which I never even touched the engine - it just had regular services and the only faults were the running gear and it's now lying distraught having failed its MOT nine months ago - it will be a subject for some recycling as I suspect that a lot of its bits will fit the Micra (same registration year), I had to buy a new plug socket for the K11, everything a little too tight a fit, obviously.
Oh, the joys of driving...
 
Having changed the air cleaner and plugs and it seems to have improved considerably. Certainly no signs of pre-ignition and much improved low revs acceleration - only goes to show how bad the air cleaner was - I must admit it didn't look that bad!

I still notice that the exhaust tailpipe isn't nice and grey even after a 20 mile journey - I suppose I'll have to do a motorway trip and see what happens. And still no sign of the fan running.

oh, well...
 
Why did the fusebox melt?! I'd be more worried about that! :laugh:
I'd sort that first as there could be other circuits running thru it that affect the fan.

If you leave the car running, heater blower off and heater in the hot position does the car start to overheat?

Is the coolant level ok? Bled thru ok?

Does the heater work? Coolant relatively clean? If coolant isnt circulating correctly past the sensors how can it know how hot the coolant is?
 

Similar threads

Slug
Radiator Fan?
Replies
1
Views
2K
Shaun
Shaun
S
K12 Radiator Fan INOP
Replies
0
Views
830
sun130
S
T
Radiator fan
Replies
3
Views
888
Micratec
M
C
Micra overheating no fan
Replies
5
Views
954
Chillidad
C
W
not overheating but radiator cold
Replies
4
Views
1K
Shaun
Shaun
Back
Top