Cooling fan questions

[andre]

Hi all

I have been scratching my head over the operation of the the electric cooling fan for a while and was wondering what other folks have experienced.

In traffic my car will heat up to about two ticks over 90 on the gauge then the fan will kick in (along with the lurch as the ISV does it's thing). The fan runs at a pretty high speed and only spins for about 20 seconds or so. The temp does come down a fraction, but a few minutes later the fan will kick in again and so we bound down the road with the crawling traffic.

Now the odd bit, if I switch on the aircon the fan comes on at a much more sedate speed (as expected for the aircon operation). This also serves to stabilise the temp at about two ticks under 90 on the gauge. And there it will stay unless it is really hot outside and I am moving really slowly in traffic. I normally do this on hot days, but it is a bit of a pain in the cold.

Now the question is. Do other folks have the same behaviour. It seems to me that it would be much better to have the fan kick in at the slow speed when the temp is lower and then only kick in the turbo option when the temp goes higher still. I have heard that the fan is a three speed job and has another speed that is supposed to come on if the temp is around 120, but have never experienced that myself.

If my operation is normal, how would one go about changing it to operate at the lower speed first ? Is it the ECU that controls the fan or a simple machanical temp sender ?

Thanks for the help
Andre

[Martynf]

H Andre,

Nothing you've said sounds out of the ordinary! well except for the "two clicks above 90" that seems a little high. BUT, I bet all of our temp gauges show different temps, IE my fan comes on when the gauge shows 87.

Maybe... just maybe.... either the rad fan switch needs replacing if the speed one setting has packed up, might as well change this, its cheap and easy to do. Also.. there is a 'metal plate speed controller' bolted to the chassis of the car same side as the rad, it's worth checking that all the wires are indeed actually on the speed controller? if one is off, that would explain maybe just the one 'high speed' fan operation you have.

The fan kicking in every 20 seconds sounds about right in very hot stationary traffic, especially in SA where I bet its a lot hotter than the UK!!

Fan always comes on at a low speed when AC is on, this kinda suggests that the speed controller is working and that the fault is the rad fan switch. Change the switch and check the condition of the wiring to it. If that doesn't sure the problem, then maybe the fan relay is at fault, unlikely....

This should be a simple problem to fix. Change the rad fan switch, check the wiring at the plug. Check the wiring to the speed controller on the chassis. Look for a metal plate with terminals off it. If none of thse cure, maybe suspect the fan relay.

HTH
Martyn

[Dr H]

I have no air con but my fan works exactly the same. Normal temp (moving at decent speed) 2 clicks below 90, stationairy traffic cuts in at somewhere between 1 and 2 clicks above.

Never gets any hotter than this even when the outside temp was up in the 30s this summer, and as far as I know has never come on at the higher fan speed.

[porkkis]

Does someone still think the aux rad is needed? :confused: :confused:

[Doug_RS2]

Originally posted by porkkis
Does someone still think the aux rad is needed? :confused: :confused:

I am thinking of removing the aux radiator - I think I could get a lot more airflow into my cone filter with an angled deflector in place of the rad. It would also direct more air to the aircon/main radiators.

I might just block the 2 hoses to the aux radiator (it is definitely in parallel to the main rad?) and see what temps it starts running.

Doug

[andre]

Hi Martyn

Just a question on your experience. When your fan comes on at 87 is it the Rolls Royce turbo fan or the gentle sea breeze (aircon) setting ? I have this distinct feeling I am missing out the first speed all together, but then from what LPHUK2002 says, maybe not.

Thanks
Andre

[Martynf]

Andre,

I understand what you mean, the AC speed of my fan is slower than when the fan comes on at about 90 degrees. I don't think my has ever used full speed!!

Martyn

[Markus]

If I remember correctly the radiator fan in the S2 works something like this:

The fan has three speeds:

Speed 1: This one is only triggered by the AC and the after-run (sometimes called Turbo Coolant Pump) cooling switch. This speed is NOT triggered by rising coolant temperatures while the engine is running.

Speed 2: This is triggered when coolant temp. rises above 95 deg. C.

Speed 3: This is triggered when coolant temp. rises above 102 deg. C.

My guess is that most people haven't ever had their fan running at speed 3. And so it should be, since speed 3 is actually an "emergency option" designed to kick in if speed 2 doesn't manage to keep the coolant temp. down. Speed 2 is however also very noisy and might therefore be mistaken for speed 3.

This is what I remember from experimenting with my (not working) after-run system. Might not be completely correct though. Remember to check s2central.net and the SJM-site for more info on the cooling system.

[s2driveruk]

You can get some cracking stares from people when the fan kicks in on these cars. I have had the 2nd stage fan (turbine ) after running with aircon on during the hottest days, but after about 30 seconds of turning off the aircon, the fan drops back to the normal one.

If you can, check all the wiring to the motor as it pulls a stonker of a voltage directly and (as i found out) it managed to fry half my loom and the fusebox. Ensure all the contacts are clean, the wires are in good condition and the earthing is good. otherwise expect something like a £550 bill

David

[andre]

Hi guys

Thanks all for the replies. Sounds like my fan is working as it should be, with maybe the on/off temp being a bit high. I'll look at checking all the wires and maybe swapping out the sender unit (anyone know where it is off hand ?).

David, you sure are correct about the current drawn by the fan. On idle it actually loads up the altenator to such a degree that the ISV jumps in to bring the revs up again (on my car at any rate).

Anyone know if it is possible to "test" the fan speeds by bridging out contacts somewhere ? I would love to know what speed 3 is like :eek2:

Thanks
Andre

[dan_b]

this is exactly what I get with my system (the "manual aircon" from the 91 car), and it is normal.

In the last few weeks with it getting a little cooler now, if I keep the air con on (as I was told to do after I had the system re-charged a few weeks ago to make sure the system is kept lubricated), the continual action of the low speed fan has had the effect of reducing my obvserved coolant temperature to about 65 and keeping it there, even in traffic.

[Markus]

Check out the SJM-site:

http://www.sjmautotechnik.com/cooling.html#fan

Might however differ slightly from the S2.

EDIT:

dan_b: Coolant temps of 65 deg. indicate that you have a faulty thermostat. Of course it could also be your temp gauge showing false readings, the multifunction temp. sensor that gives the signal to the gauge is known to fail (and therefore often called multi-MAL-function sensor...).

[andre]

Cooling fan update

Hi all

Thought I would just let you all know the results of my cooling fan investigation this weekend.

----
Quick recap: "aircon" mode fan worked fine, car heated up to two ticks above 90 in traffic then "turbo" mode fan came on for a few seconds. Often used aircon to keep temp at 90 in traffic.
----

After reading the S4/6 related stuff on the SJM site Markus added (great info there, BTW, thanks Markus) I set about testing. Turns out that one of the wires from the sender unit was cut. It was the second speed wire so my car was actually always only making use of the "emergency" speed. Not good at all !! Quick bit of solder and some tape and now things are like they should be. In traffic this morning the car never went above 90, where before it would have been sitting at the two ticks above mark all the time with the turbo fan coming on every few minutes. You have to listen quite closely to hear the stage two fan working now, but you can sure see the effect.

So to all those folks out there that have to use your aircon to control the heat of your car in traffic or if you can easily hear your fan come on - CHECK YOU SYSTEM !!! If you want to hear the difference between the two speeds check out the SJM link for a test procedure, it's really easy and all you need is a bit of wire to short out the plug from the sender unit.

The knock on effect is that now, when I get home after being in traffic for a while the turbo cooling pump cycle is not activated since the car is not so hot. This always used to happen before and can not be good for the turbo in the long run.

Thanks to all those that helped.
Andre