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        General >> Problems >> crazy radiator fans 
        
(Message started by: catalina on Jan 28^th, 2012, 10:25pm)

Title: crazy radiator fans
Post by catalina on Jan 28^th, 2012, 10:25pm

On my cosworth, both radiator fans stop and start erratically. They start even when the engine is cold, maybe will run for 2 minutes, then stop for a few minutes, then start, stop etc,etc,etc.
Also, the AC light comes on for no good reason, but the fans seem to stop and start irrespective of whether the AC light is on.

I have changed the large green relay situated behind the offside headlamp. Also the temperature sensor situated on the top hose at the front of the engine. Also tried disconnecting this temperature sensor. No difference; the fans still start and stop erratically.

Can anyone tell me where the gubbins that controls the fans is located. Is it the unit just below the temperature sensor, which seems to have a complicated ribbed plastic cover from which wires exit? Does this cover come off? If so how? The wires enter a 1 cm dia ribbed plastic ducting. (I have no idea where the other end of this ducting is).

The engine never gets up to normal temperature but I want to solve this fan problem before I consider replacing the thermostat situated behind the AC. compressor.

Are there perhaps any clear circuit diagrams for the cooling system?

Any advice would be much appreciated. I'm getting hypothermia, without the heater working efficiently.

Cheers

John

Title: Re: crazy radiator fans
Post by Tompion on Jan 28^th, 2012, 11:14pm

The green relay is controlled via the engine management.

Presumably you have climate control & you turn the AC off when you turn on the ignition (it defaults to on at start up – unless it was less than an hour since you last ran the car with the AC off).

The problem with the AC coming on may be caused by a dirty or worn blower speed selector or it may need a reset. This isn’t a switch it’s a variable resistor. As you’ve probably noticed when you turn the AC to manual then back to auto the AC comes back on even if you’d turned it off before. So you can have a situation where the resistance effectively changes because of a dirty selector from auto to manual and back to auto which causes the AC to come back on.

To try a reset:
http://www.fordscorpio.co.uk/ccreset.htm

When the AC is on it cuts in and out all the time, when the AC clutch is commanded on the fans come on at low speed straight away however they don’t go off for several seconds after the AC clutch is commanded off.

The AC will be on if you have the air distributor turned to windscreen regardless of whether the AC light is on.

The engine should get up to temperature even if the fans are running.

Title: Re: crazy radiator fans
Post by PJDavis on Jan 28^th, 2012, 11:29pm

What car do you have? I suspect you need to change your thermostat. I have a 2.3 and somewhere on this site I have posted-up a fairly easy way to change the thermostat, but I'm a 'numpty' and can't post you a link! When I start my car in the morning, it automatically selects the AC because the dial is on windscreen-clear. The Fans will come-on at half speed when the AC is on, and even if the AC isn't on they will click in-and-out at half speed depending on their whim! You'll know when they're at full power, you'll hear them! This happens rarely, I drove my car over to Italy, then Sicily and finally to Malta in 2010, and the full power fans only came on about half a dozen times, this in August the hottest time. The car was fully loaded with stuff taking it across to our place in Malta, and never failed once. I have put an extra switch in my 2.3 to control the two fans at full power, so I can manually put them on or to default so I knew I could control them for the journey, never needed to use the manual switch. I live very North Scotland, extreme temperatures, and don't have a problem, I would say your thermostat.

Title: Re: crazy radiator fans
Post by PJDavis on Jan 28^th, 2012, 11:35pm

Good stuff from Tomp. I fully agree. Your temp-gauge should sit in the middle or just below. Mine did throughout the journey abroad.

Title: Re: crazy radiator fans
Post by Simmo on Jan 29^th, 2012, 6:47am

Peter. He says he has a Cosworth and talks of the thermostat being behind the air con compressor so that is a major problem of access and to source.

Re links. Check your PM's. ;) Mike.

Title: Re: crazy radiator fans
Post by PJDavis on Jan 29^th, 2012, 11:25am

Yeah, I must be blind!! ::)

Title: Re: crazy radiator fans
Post by catalina on Jan 29^th, 2012, 11:41am

Thanks guys. Your advice about the AC seems to be spot on Tomp. The selector switch is hit and miss so clearly needs a clean. However this still leaves me with the radiator fan problem.

When you say that the green relay is controlled via the engine management does it mean I've got to take the car to Ford? Is there nothing I can do myself?

My first reaction , I think, is to disconnect the fans completely. If, as you hint, the engine still won't get up to temperature, I suppose I've got to change the thermostat. I've been there before on a previous Cosworth, but then Ford destroyed the vertical hose and spent 9 months and a fortune finding and replacing it, then destroying the inlet manifold gaskets. So you'll understand my reluctance to jump straight in with the thermostat. I see that there is a step by step guide to thermostat replacement somewhere. So I'll supervise my local garage doing the job on there ramp!!!!! You learn the hard way!!!

So the question is - how do I get the fans working correctly? Unfortunately my knowledge doesn't extend as far as dealing with an engine management system.

Title: Re: crazy radiator fans
Post by Tompion on Jan 29^th, 2012, 1:03pm

You could check behind the climate control panel to make sure the ribbon is properly latched.

When I said engine management it was just to distinguish from “the gubbins that controls the fans” I don’t mean there’s anything wrong with it, it’s just reacting to information it receives from either the aircon or the engine coolant sensor.

I’m not familiar with the Cosworth, may be you disconnected the gauge sender? With my 2.3 if I disconnect the ECT the fans come on, the engine coolant sensor is here:
http://www.fordscorpio.co.uk/manual/engineman/cosworth/24vECT.pdf

Have a look here:
http://www.fordscorpio.co.uk/coolfans.htm

You could disable the AC I think disconnecting the Pressure Switch will do that, scroll down the page of this link to find the location of the pressure switch plug.
http://www.fordscorpio.co.uk/airconelectrical.htm

Title: Re: crazy radiator fans
Post by Simmo on Jan 29^th, 2012, 2:49pm

Before you go rushing to any garage you'd better be sure you can source a 'stat. They are a rare find and very expensive IF you can get one.
UPDATE. There's one listed Here (http://www.fordpartsuk.com/shop/ford_scorpio_cosworth_29v624v-thermostat_1073.htm) at almost £113 with VAT !!.

Title: Re: crazy radiator fans
Post by catalina on Jan 29^th, 2012, 9:30pm

Thanks again Tomp. I'll have to spend some time studying this data. The answer is probably in there somewhere.

Simmo, I am almost certain that the stat advertised is not from a 24v Scorpio Scorpio Cosworth but from the earlier Granada Scorpio. Ford agents usually confuse the two.

Fortunately, my old car is a donor for my latest car so I have a stat which is only 2 years old.

For your info, I have just driven the car with the fans disconnected (removed the large green relay) The engine heated up much quicker and to nearly half way on the temp gauge. Then left engine running for 1/4 hour with gauge getting almost to the red. Car heater was great. The good news seems to be that the stat is ok. :)

Get the impression that constantly running fans are limiting the effectiveness of the stat to retain heat in the engine block. There's a by-pass to the stat isn't there? Perhaps this allows some water to circulate through the radiator which the fans are then cooling thus keeping the engine temp low.

Hope my search through the data you sent me will solve the problem with the fans before the hot summer weather arrives!!

Title: Re: crazy radiator fans
Post by Tompion on Jan 29^th, 2012, 11:38pm

Page 22 of this manual (page 24 of the PDF) shows no circulation through the rad with the stat closed here:
http://www.fordscorpio.co.uk/cgi-bin/yabb/YaBB.pl?board=admin;action=display;num=1290587487

I know people are usually given the wrong pump for the 24v, not heard of the same with the stat.

My 2.3 used to stay cold with the AC on until I changed the stat. Airlocks in the matrix hoses have had the same effect (staying colder with AC on) as did a partially/fully blocked matrix (don’t get the airlocks since changing the matrix).

I rarely turn off the AC & the gauge is horizontal within 1.5 miles regardless of the weather but the 24v may be different.

Title: Re: crazy radiator fans
Post by catalina on Jan 30^th, 2012, 2:51pm

Thank you for all your advice Tomp. The manual is great and I take your point on the stat. I will probably try changing the stat. However, I still have to sort out why the fans run at odd times.

John