cooling fans

[kirk pearson]

hi i am sure this has been asked a thousand times but here i go!
we have a 2 litre petrol 2wd that's had a temp gauge issue, going up and down and showing hot when cold ect, i have replaced the single wire sensor next to thermo housing and its cured gauge issue 100%.

the issue...
cooling fans behind radiator are on permanently, this was the case before and after the sensor was replaced.
does it when ac is on or off regardless

there is a "low coolant sensor" system/light and its off on the dash[light is off] and there is enough coolant in system

is there a rad fan switch located in rad? or is fan ecu controlled?
i assume the faulty temp guage sensor has put ecu into default "fan on " mode?
any help or thoughts greatly appreciated
regards kirk.

ps i am a garage and its a customers vehicle and i don't want to waste his money chasing what might be a well known easy fix, thanks again

[g8dhe]

There are TWO coolant temperature sensors;
The single wire one at the top of the engine ONLY drives the gauge, nothing else.
The two wire one down the side of the engine feeds the ECU which controls the Fans.

The cooling fans are also operated by the A/C, on mine they seem to be on fulltime, but to be honest I haven't really checked what happens when driving along!

There is also the Scavenger fan that is used to blow air thru the engine housing, its sensor is mounted at the top of the engine housing under the handbrake, this is normally only required when the vehicle is static and air isn't flowing thru the engine housing from forward movement.

[teenmal]

Hi Kirk, it does sound like a faulty ECT sensor-related fault as a matter of interest has this fault ( continuously running fans) just developed or was it present when your customer purchased the vehicle.

[kirk pearson]

i believe the fault has existed since time of purchase,

[Bob]

Welcome aboard.

I wonder if someone has wired the fans to run continuously, possibly fitted a switch which is in the 'on' position?

Don't quite understand the low coolant sensor is 'off on the dash (light off)'? The light would be off if there is enough coolant.

If it's one of Hayden's it will self test when you turn the ignition on, just a second or two 'beep'.

[kirk pearson]

the low coolant light is "off" and there is enough coolant, i assume the light comes "on" in the event of low coolant
i have searched for a override switch and cant see one.
oh and thanks for the welcome

[teenmal]

the low coolant light is "off" and there is enough coolant, i assume the light comes "on" in the event of low coolant
i have searched for a override switch and cant see one.
oh and thanks for the welcome

Personally, I would check out the ECT sensor and connector first.

[kirk pearson]

update.....
found a plug dangling near thermo housing, its a two wire and fits onto a sensor just under the thermo housing, that has stopped the fans running all the time so i guess someone forgot to re connect it for some reason
next issue is that the temp rises as expected and after a while the scavenger fan comes on and off but its not enough to cool the engine so for some reason the main fan[s] at the front aren't being activated.
you can get round it by switching a/c on-that turns fan[s] ? [not sure yet] and it cools accordingly.

[g8dhe]

The scavanger fan isn't designed to cool the engine itself, its designed to flush (scavenge) the heat out of the engine HOUSING. The radiators fans cool the coolant so that the thermostat can feed cooler coolant back into the engine as its temperature rises.

Yes the scavenger fan will have a small affect on the internal engine temperature but that is NOT its purpose.

Whilst you have reconnected the ECU to its temperature sensor, maybe the sensor is faulty and hence it was disconnected to force the fans on ?

[Bob]

You're correct about the coolant alarm.

If you wanted to test it you could suck out some coolant with a turkey baster or similar then turn on ign.

[kirk pearson]

lol i WILL get to the bottom of this, can anyone tell me which fan is which at the front, ie, is there an A/C one and a coolant one ?

[Bob]

Mine's diesel, but the two fans fitted immediately behind, and to, the radiator draw air through the rad and air con condenser.

They work together, not one for rad & one for a/c.