Engine cooling fan not cutting in - any advice appreciated

[Mutley00]

I disconnected the two leads to the Otter Switch and held them together but still no joy. Whats should be my plan of attack please? Is there a fuse for the fan as I cant find one listed in the handbook. Thanks in anticipation, Andrew

[v8s4me]

Hi Andrew - have a look at the thread below this one. That tells you what to check for. The fuse and the relay are probably on the same board. Look under the dash on the left hand side, behind the glove box. Pull away the carpet and it will probably fall into the foot well.

[Mutley00]

Thanks for such a prompt and helpful reply matey. Have a good Christmas, Regards, Andrew

[phillpot]

Not far from the fan motor you'll find some connectors, quite possibly broken or corroded. See if you have 12v there or apply 12v directly to the fan motor see if it runs.

[Penelope Stopit]

Before disturbing anything

The first thing to do is have someone inside the car listening for the fan relay clicking in and out as you make and break the Otter switch circuit at the Otter switch

Post back the result and someone will help you further

[Oldred_V8S]

phillpot said:

Not far from the fan motor you'll find some connectors, quite possibly broken or corroded. See if you have 12v there or apply 12v directly to the fan motor see if it runs.

As MIke says, supply 12v to the connector to ascertain if the fan runs.

You could also stick the probes of your meter into the plug of the fan (with the fan connected and the otter switch shorted) to see if you get ~system voltage. This will tell you a lot about the circuit.

You will either have no voltage (or extremely low), or nearly the same voltage as the battery is putting out. Let us know the results and we can help further.

The test below is not a good use of your time.

Penelope Stopit said:

Before disturbing anything

The first thing to do is have someone inside the car listening for the fan relay clicking in and out as you make and break the Otter switch circuit at the Otter switch

[v8s4me]

phillpot said:

Not far from the fan motor you'll find some connectors, quite possibly broken or corroded. See if you have 12v there or apply 12v directly to the fan motor see if it runs.

If you apply 12V direct to the fan as Mike says you can very quickly if the fan is faulty. This is worth doing first just to rule out the fan as the problem. The big orange fan on these cars is pretty reliable and it is unusual for one to fail. However they are very old so well worth checking out to make sure it's OK.

Once you know the fan is working you can start checking off the other likely problems.

When my fan failed on a EuroTour I checked everything except the relay. Guess where the problem was?

[Mutley00]

Thanks for all your advice chaps - much food food thought and action plans for post Xmas Day. I must admit I had a seriously worrying moment which will hopefully amuse you, when I thought that the S3 I've just bought (that had been laid up for two years), didnt have a fan at all! On my Chim, the fan(s) sit behind the rad whereas on the S3 (mine anyway) it sits in front of it, or so I've just found out with the use of a torch in the dark!. Puzzlingly, before I humiliated myself on this forum, several images on Google appear to show S series cars with fans behind the rad. Again, all thoughts appreciated.

[Penelope Stopit]

Glad to possibly be of some help

Have a nice Xmas

[phillpot]

Early S's were engine side with a cowl, later cars have fan in front of rad in an orange housing. Some cars may have replacement after market fan either side.
Obviously you carried out a thorough pre purchase inspection 🤣

Edited by phillpot on Wednesday 25th December 07:42

[DamianS3]

I like the diagnostics info already given so wont add anything..

A common failure point is the wiring as it goes under the chassis to the fans.. its pretty exposed an probably only protected with insulation tape if at all.

Happy Christmas

Damian S3

[Mutley00]

phillpot said:

Obviously you carried out a thorough pre purchase inspection ??

I thought I had, but I must admit as soon as it emerged from the chaps garage I decided I wanted it and was a tad averse to looking too hard for things that may have put me off. When SWMBO said 'Wow!' that was the clincher. It was SORN'd and didn't have an MOT, so a decent test drive was out of the question.

Thanks again for all the advice, I'd start tinkering today except my team are rather overachieving in The Prem at the mo, so football beckons.

Edited by Mutley00 on Thursday 26th December 10:07

[v8s4me]

Mutley00 said:

.... I'd start tinkering today except my team are rather overachieving in The Prem at the mo,...

You're playing my lot today so that "over achievement" should continue without too much trouble

[Mutley00]

I dont share your confidence matey. I know Nigel Pearson very well and I wouldn't like to be in a yellow shirt after 90+ mins if I'd underperformed. This is the man that told me 3 months ago he'd done with professional football, so I wouldn't mind seeing your wage bill at the year end to see how much he's getting paid, especially if he keeps you up. May the best team win as they say.

[phillpot]

I think that's quite enough of that football nonsense, this is a car forum 🤣

[magpies]

Mutley00 said:

I dont share your confidence matey. I know Nigel Pearson very well and I wouldn't like to be in a yellow shirt after 90+ mins if I'd underperformed. This is the man that told me 3 months ago he'd done with professional football, so I wouldn't mind seeing your wage bill at the year end to see how much he's getting paid, especially if he keeps you up. May the best team win as they say.

And guess who I'll be supporting at 17:30

[Mutley00]

Started my investigation today (which got curtailed due to rain), which ended up just having time to remove the trim panel and exposing the Fuse and Relay board. I spotted the remains of a 30A in line fuse which has blown and melted the rubber holder. Any clues as to what it could be for? Thanks

Edited by Mutley00 on Friday 27th December 17:45

[Penelope Stopit]

Could be for any of the following depending upon what's fitted to your car

Clock, Interior Light, Hazard

Engine Run Sensor Supply

Engine Cooling Fan Relay Supply

Dim Dip Module

---

Could be that the fuse-box is damaged and the wiring has been cut away from it then an in-line fuse holder fitted to do the same job

Wonder if it's the Brown/Blue for the radiator cooling fan fuse that's been cut out of the fuse-box

This would make sense, see below diagram, Brown/Blue = NU

Is there a Pink cable connected to the other side of that fuse-holder that supplies the radiator cooling fan?

[GreenV8S]

It's non-standard. At that rating it is likely to be headlights or fan. Given the problems you're looking for, it's reasonable to assume it is for the fan. The fact the holder has overheated suggests you may have had a poor connection between the holder and the fuse, so check the state of the contacts before you try replacing the fuse.

It would also be worth checking the condition of the fuse box to see whether a fuse holder here has been bypassed - if so, I'd want to check the state of the other fuse holders in case this is a symptom of a more general problem. If the car has been left damp, corrosion can cause widespread electrical problems.

[Penelope Stopit]

Going to go for radiator fan possibly drawing too much current through an in-line fuse holder or cheap and nasty fuse-holder

Same problem very likely overheated the original fuse holder, too much current is a melter

A tight/bad fan motor drawing too much current could have been replaced sometime in the past

Is the fan free? can't remember if you mentioned the fan motor being free

Not fit to read all the way through the posts as I'm very close to being drunk, too much Cognac on top of a good smoke