Cooling fan not coming on

[Nova_Tek]

Not on the Nova but the engine is the SEH on a Cav.

The cooling fan stopped working about 2 weeks ago. Now the fan switch which screws into the rad was known to be on its way out and was leaking. Driving at speed was fine as the cold air would sufficiently cool down the coolant but in town as you can guess the temp would rise quickly but no fan would come in. Just recently in the last week the fan started kicking in but intermittently. So it would work on one journey but not on the other.

As the fan switch was old, rusty and leaking we fitted a brand new one yesterday and also changed the CTS as that had never been changed and we suspected it was on the way out as the car would sometime run a bit rough when warmed up.

Everything was changed over, we filled up the cooling system with antifreeze and water and fired her up. No leaks everything was going fine. One problem, come 90deg on the dials (where normally the fan would kick in) nothing :mad:

I just disconnected the fans power supply plug and ran a 12v supply to it, and it came on no problem. Fuse is fine too.

What else could this be? Brand new CTS, brand new fan switch, had a thermostat changed about 15k miles ago, fan tested and came on with a 12v supply.

I'm baffled and quite frankly pixxed off

Thanks :thumb:

[Asa-James]

faulty fan switch? try running the car up to temp and see if it has continuity over the switch, i've seen it before with a new dealership fan switch on a punto, went thru 3 before we got one that worked (faulty batch apparently...)

[Nova_Tek]

The fan switch that screws into the rad right? Well with the old one on the fan came on fine, the fan stopped coming on 3 weeks ago, then started intermittently working last week. I don't think the fan switch is the issue tbh. Can there be anything else, apart from what I mentioned, that can stop the fan from coming on?

[Asa-James]

bad earth? i know its cliche, but worth checking. other than that, any and all connections for cleanliness/security. the fan only works with a 12v feed, switched thru the thermo switch (on the rad)

not entirely sure if it would have a relay, you'd need to check haynes/owners manuals or pick someones brains on here who know more about the electrical side

[Nova_Tek]

Have done some general cleaning and checking of plugs and connections. None of the connections seem to be damaged and the rad fan switch came with a brand new plug and wiring so that's mint.

Will check out the earths.

Hopefully the other png boffins will take a look and add to the thread.

:thumb:

[AlexW]

Got access to a multi-meter? I seem to remember the rad switch is neg switched.

i presume they deffo comes on at 90degrees? i know corsa's done switch on untill 98ish iirc.

Only other thing to check is to take the rad switch out (Maybe plug the hole with the old switch?) And check the resistance between the pins when off is a fair amount (make a note or just have a good memory) and then put a bit of boiling water somthing so the sensor end is in but you can still get to the pins and then check resistance between the pins again, should be 0 or close to 0.

New dont always mean working.

[Nova_Tek]

Not got access to a multimeter.

I see what you are saying about it may not work but I strongly feel that if the car was driven around it would work like the old switch i.e. intermittently.

The Cav, as far back as I could remember, has always come on at 90 on the temp guage. It never ever went above 90. Recently even with all the original bits it was sailing past the 90 hitting 100 with 110 being the danger zone. My bros Cav which is the facelift (XEV) runs very differently compared to the SEH as that comes on at 97 deg on the temp guage.

The engine has had a compression test and it's perfect. So I'm eally stumped. Would it be worth removing the fan plug and getting a multimeter on it and to see if there is any supply coming when the temp guage reads 90? Or alternatively I could remove the new fan switch plug take a reading when engine is cold and a reading at 90 deg pretty much what you said but without loosing new antifreeze lol

[Asa-James]

it should always have a supply, the switch has a bimetallic strip inside that completes the circuit at a certain temp. it could be the switch is defective if its now not working at all, or you have been supplied with the wront temperature switch that doesnt kick in til a much higher temp

[AlexW]

The intermittent could be the switch, I cant see it being wiring, but it might be.

I doubt its the fan as it was working ok.

Edit: Accually asa you might be right, if the switch is for a later one get the car up to 100degrees. If you need to use the car bridge the pins.

[Bubba]

my old one was wire up to a permanant live...

[eightvalver]

I had the same problem with my Cav, and on another Fiat i had, i too changed the thermostat and switch etc... but it turned out to be an air lock in the radiator or somewhere else in the system.

Maybe worth trying to bleed the system properly?

It also could be the water pump, if it is worn or broken then the coolant cant get around fast enough at idle speed, so you could try giving the engine some revs?

[Nova_Tek]

Water pump was changed about 9 months ago. Airlock is possible but that must mean that there was an airlock before I changed the switch and now again after draining the rad and refitting the switch. I filled up the cooling system and let it run with the cap off till it got upto temp i.e. 90deg. Pretty much what I did the other day to the other Cav after changing the rad and thermostat.

I'm gonna get a multimeter tomorrow. Gonna remove the actual fan power supply plug from the cars loom and take a reading whilst engine is on but cold. Then at 90 deg take another reading which should show power going to the fan as that's when the fan should come on.

Just to eliminate the rad fan switch and wiring.

[eightvalver]

I filled up the cooling system and let it run with the cap off till it got upto temp i.e. 90deg.

If you run it up to temp with the cap off, doesn't that mean there is no pressure in the system so the coolant wont flow fast enough? Unless you mean you did that while bleeding the system..

-just checked my haynes, and states the thermostat starts to open at 92deg and is fully open at 107deg and the fan should switch on at 100deg, and off at 95deg (all models) that did surprise me

[Nova_Tek]

Yeah whilst bleeding the system.

Well I'm purely going on the cars characteristics for the past 18 years lol.

So 92deg thermo opens water flows into the rad and at 100deg the fan should come on.

Will run the car and wait till 100deg on the guage to see if the fan kicks in. If not then there is an issue.