ECU information required

[Rhinoman]

I've had a go at characterising the WTS:



I'm currently rebuilding my lab, when thats done I'll start putting actual temperatures inton the code based on this graph.

[widdowson2008]

Not English yet, but definitely closer.

[mikexgough]

Not English yet, but definitely closer.

Be nice to see the findings of this....

[Rhinoman]

I've been Bongoing around Cornwall, hopefully I'll be able to have a test of the engine bay sensor this week.

[stockportdave]

The temp vs resistance graph is much appreciated. I have just checked mine at 19deg C and get about 2.7k and less than 200R at 95deg C. I phoned Bongobits who very helpfully measured one, off-the-shelf. Their reading was 700R. Which made me think my temp sensor was faulty. Seems it isn't, from your figures, which is a bit upsetting because it might be my ECU.

History: on holiday, engine overheated to block temp of 105deg C (I have an oven temp sensor/alarm stuck on head of block). AA man came and he noticed that the rad fan was not on, disconnected the sensor and both fans roared into life. Now back home I have put a 1k variable resistor in place of the sensor and now the fan is on all the time! from 0 ohms to 1k to open circuit.
My air conditioning packed in about 6 months ago. Any suggestions?

[Rhinoman]

The rad fan is switched by a relay, I would start by checking the relay and then perform the variable resistor test while monitoring the relay coil driver from the ECU.

[mikexgough]

wasn't sure about my fan sensor last week, so I changed it today, the plastic connector was "rusty" brown looking ...BUT I have not tested it..........I did run the motor after until it "fired" up the fans........needless to say they worked when the connector was removed........I think from previous posts on the forum and the manual that the fans "kick" in at a coolant temperature of 108 C

[Rhinoman]

If you disconnect the sensor the voltage will go outside of its programmed limits, clearly the ECU then bangs on the fans as a default.

[stockportdave]

thanks chaps - News from under the hood..... The range of the resistance is critical. Just increased pot to 10k, at about 2.7k fan is not on at start up (hurray!). As i reduce the resistance to simulate increase in temp (engine ingnition on but engine not running) I hear first a relay come on near the top of the engine and then as i continue to decrease the resistance a relay under the hood. All as you would expect (?) but .... No fans start.
Will keep you posted.

[stockportdave]

PS - I think coolant runs at about 85deg suspect fab kicks in around 87 ish

[Rhinoman]

thanks chaps - News from under the hood..... The range of the resistance is critical. Just increased pot to 10k, at about 2.7k fan is not on at start up (hurray!). As i reduce the resistance to simulate increase in temp (engine ingnition on but engine not running) I hear first a relay come on near the top of the engine and then as i continue to decrease the resistance a relay under the hood. All as you would expect (?) but .... No fans start.
Will keep you posted.

Any idea of what voltages the fans switch on at?

Have you checked the fuses?

[stockportdave]

Thanks Rhinoman

Latest info:

Just redid tests, as before relay comes on as I decrease resistance but this time i continued to decrease the resistance - the fans do eventually turn on. At sensor resistance of about 153R. When I test my sensor I get 70 deg = 435R, 98 deg =190R

Thanks for your info mikexgough - are you sure about this? I know water boils at higher temp under pressure but I wouldn't have thought the pressure was that much.

Does anyone know what resistance should be for fan turn on?


ps - both fans start together, I thought they might start with 1 fan then 2 if temp not stabalised - save on fuel.

[Rhinoman]

How are you testing the sensor? there is a big thermal lag that can make it difficult to get an accurate reading. I found that the best method was to boil the sensor for a few minutes and then record the temperatures/resistances as it cools, a temperature stabilised oven/cooler would be best.

The boiling point is increased both by pressure and by antifreeze it'll be something like 125C.

[mikexgough]

The water sensor test in water according to the book of words......is 20C is 2,3~2.6 kohms and 80c is 0.29~0.34 kohms if that makes any sense to you leccy guys....
The fans are run off off ECU terminal 3Z which is Cleaning Fan control signal connected to cleaning fan relay No3 and when the ignition is ON & the fan NOT operating (coolant below 108C) is 12v and when Fan operating (coolant above 108C) is below 1v if that also makes sense......to a mechanical guy like me......if the fans don't run.....change the switch.....
On your Aircon problem with it not working.....it seems common that all is well with the system in the main, the biggest and most common issue is lack of refrigerant gas.....

[Rhinoman]

The water sensor test in water according to the book of words......is 20C is 2,3~2.6 kohms and 80c is 0.29~0.34 kohms if that makes any sense to you leccy guys....
The fans are run off off ECU terminal 3Z which is Cleaning Fan control signal connected to cleaning fan relay No3 and when the ignition is ON & the fan NOT operating (coolant below 108C) is 12v and when Fan operating (coolant above 108C) is below 1v if that also makes sense......to a mechanical guy like me......if the fans don't run.....change the switch.....
On your Aircon problem with it not working.....it seems common that all is well with the system in the main, the biggest and most common issue is lack of refrigerant gas.....

The resistance readings I got tally with the test in the manual.

The relays are switched on the ground side so the 12V is measured through the relay coil, when the ECU switches the relay on the terminal goes to 0V/GND and current flows through the coil. If the relay coil is faulty then the voltage will always be 0V but I think we can assume the coil is OK as the fans can be made to switch.