Does anyone have a wiring diagram for how the low and high-speed modes of the cooling fan (radiator) is connected?

Looking to find which fuse and relay it is connected to?

The cooling fan only appears to work when the AC is turned on

The fan is controlled by the ECU if it’s working with the aircon then there is no reason it wouldn’t other wise work, there are no separate relays or fuses.

Unless the car is really hot the fan won’t generally kick in, next time after you’ve been on a long drive and you get to your destination or home. Pop the bonnet and sit with the engine running for 10 minutes or so, it should almost certainly then kick in (aircon off obviously)

AndyRKett said:

The fan is controlled by the ECU if it’s working with the aircon then there is no reason it wouldn’t other wise work, there are no separate relays or fuses.

Unless the car is really hot the fan won’t generally kick in, next time after you’ve been on a long drive and you get to your destination or home. Pop the bonnet and sit with the engine running for 10 minutes or so, it should almost certainly then kick in (aircon off obviously)

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This was the first thing I tried. The fan definitely only works with the AC turned on!

I left the car turned on, with the AC off and it overheated (dash gave a temperature warning and the coolant started overflowing). I turn the AC on and the radiator fan turns on almost immediately and does not overheat!

Does the engine know it’s over heating.

Sounds like it need plugging in to MES then you can turn the fans on and off to test them as well as look at the engine temperature the engine ECU is recording.

The simple fact of the matter is that the fan works and it is turning on and off, which is controlled by the ECU In the same way that the engine operates the fan to cool the engine.

The only logical step is the temperature sensor is not working correctly or there is an ECU fault stopping the ECU from recognising the over heat. The latter would be very unusual.

Well it definitely boiled so my thought is this, with a over heat warning on the dash, fans that clearly work OK, leaves me to think one of two things, ECU corrupted or is there more than one relay for the fan? IE AC control relay and temp control relay? I've not got my book to look at the diagram.
In the mean time leave the AC on all the time, but then in Australia I'm surprised you turned it off.

Cars used to have a temperature sensor in the radiator to activate the fan. Isn't this the case any more? If there is a sensor (which may be visible) chances are it has failed.

TrevC said:

Cars used to have a temperature sensor in the radiator to activate the fan. Isn't this the case any more? If there is a sensor (which may be visible) chances are it has failed.

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Doesnt it use the temp sensor that gives the engine temp on the dash as the dash is saying overheating to activate the cooling fan via the ecu?

I would have expected an overtemperature sensor to be mounted on the head or the block, as this would operate if the thermostat stuck shut, and in that instance the radiator would remain cool. Cooling fan actuation sensors tend to be on the rad.

TrevC said:

I would have expected an overtemperature sensor to be mounted on the head or the block, as this would operate if the thermostat stuck shut, and in that instance the radiator would remain cool. Cooling fan actuation sensors tend to be on the rad.

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There's no sensors on the rad of our 59 plate 1.2.
Remember the fans will run with the ac this is normal whilst the compressor is operating and is separate to the "engine cooling "
Anyone know if there's two relays

Beats me then. Haynes manual?

TrevC said:

Beats me then. Haynes manual?

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It's in my shed at home

So I've had a look at the manual (for the UK 1.2) relay 6 controls the single cooling fan and relay 7 controls that ac cooling fans side so is it possible that relay 6 is faulty?

More info
with the engine way up to temp or even over, is there a earthing switching signal applied to pin 85 of relay 6? would show +12v normally and 0v approx when the fan is on(ac off, relay installed) also note the feed to the fan goes through a resistor(12 in the picture) if this has failed then again the fan would not operate normally-don't know where this is installed.

John202020 said:

So I've had a look at the manual (for the UK 1.2) relay 6 controls the single cooling fan and relay 7 controls that ac cooling fans side so is it possible that relay 6 is faulty?

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Checked that both relays are working fine!

Does the manual state what the low-speed resistor no 12 is meant to be rated to? I assume that it is meant to be 1 ohm as per the below. I checked the relay resistance and it was around 1.2 ohm

https://www.fiatforum.com/stilo-gui...engines-radiator-fan-slow-speed-resistor.html

Did you check the relay switches the contacts for the fan? a small 9v battery will operate the relay on the bench, resistor could be a culprit especially in hot climates as it will be used far more, sorry it does not state value. If you know what you're doing, you could feed the fan directly and measure the current and work out the resistor rating and either buy a new one or create a resistor bank to replace it, I had to do this on the wife's old Nissan heater blower motor. A guess at the wattage 40_50w if it drew 6a @1 ohm =36 watts
Based on 6a 4x4.7R 10w resistors in parallel will give you 1.175R total at will run hot as they're at their maximum rating each, but will cost far less ?
Also i would hope the relay contacts are far less than 1.2r as that would cook the relay?

John202020 said:

Did you check the relay switches the contacts for the fan?

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Yes, the relays are functioning and have both been replaced for completeness. Also, have tried shorting the R6 relay.

The larger R7 relay is definitely working as this is the one that is switched when the air conditioner is turned on. The R6 relay does not appear to be being switched by the ECU?

I will have to order and OBD interface and pull error codes, as well as the temperature. Maye it is a faulty temperature sensor in the thermostat?

Not certain though as I would have thought that the thermostat temperature sensor is the same one that tells ECU that it has overheated (the warning shows up on the dash)

matthewmalone said:

Yes, the relays are functioning and have both been replaced for completeness. Also, have tried shorting the R6 relay.

The larger R7 relay is definitely working as this is the one that is switched when the air conditioner is turned on. The R6 relay does not appear to be being switched by the ECU?

I will have to order and OBD interface and pull error codes, as well as the temperature. Maye it is a faulty temperature sensor in the thermostat?

Not certain though as I would have thought that the thermostat temperature sensor is the same one that tells ECU that it has overheated (the warning shows up on the dash)

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With relay 6 removed and engine ignition on, try shorting the(power) feed and out to fan pins, if the fan runs it's not the resistor pack?
As far as I can see via the manual there is only the one temp sensor

John202020 said:

With relay 6 removed and engine ignition on, try shorting the(power) feed and out to fan pins, if the fan runs it's not the resistor pack?
As far as I can see via the manual there is only the one temp sensor

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Yes, I have tried this - shorting the six relay turns the cooler on without issue.

For some reason, the car is not sending a signal from ECU?

matthewmalone said:

Yes, I have tried this - shorting the six relay turns the cooler on without issue.

For some reason, the car is not sending a signal from ECU?

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Next I would check the continuity between the relay signal wire and ecu?
Also check pin 86 on the relay socket is live(relay coil feed) when ignition is on as the ecu earth's the relay to turn it on.

Does anyone know the coolant temperature limit that the low-speed fan is supposed to kick in?

I checked with an OBD adapter and the temperature sensor is working

The temperature keeps rising past 100 degrees C???