sensor on engine??

[John the sparky]

hello,

changed my hoses today, at last

and noticed a sensor screwed into head,

above pipe that goes down to heater area (the wiggly one), on drivers side,

well on mine it's broken, and seems to have been for a while,

anyone know what the sensor is, and what to order?

thanks

John

[John the sparky]

not very technically done....

but.....




(photo is of BDC's hoses change)

[Ralph]

Didnt even know that was there you learn something new every day.

[brorabongo]

This sensor, which is in the head, just behind where you were pointing to?
If so that is the rad fan/coolant temp switch. From the above photo, you can see it's broken off, and what would happen is the radiator fans would come on, and stay on as soon as you turned the key.
My brother-in-law (Oggy) managed to change it himself, with little coolant loss. He got the replacement sensor from Bell hill garage. (great service )

[John the sparky]

yep, that's it, and yep fans have been running a long of late...

I'll call bell hill on monday, just changed the coolant


thanks

John

[brorabongo]

If you can get a helper to plug the hole whilst you change over, you might not lose much, and fingers crossed, you should be able to refill/bleed just from the bleed hose?

[bongoing-mad-simon]

hi john is this it ????
if so pm me with address and i'll send it to you , it came off old head. no charges....

or this one (2)

[roosteruk]

and what would happen is the radiator fans would come on, and stay on as soon as you turned the key.

Are you sure 'B'? Thermo switches are normally (to my knowledge,) earth switching units.
As the heat gets higher, at the required temperature, the thermo action allows continuity to the earthing properties of the engine, thus making a circuit to energize the relay, turning on the fan/s.
I would love to know the answer of this one?

[John the sparky]

Rooster, I know what you are saying and thought that myself, but the fans do come on as soon as you start it now, I thought it was different a couple of weeks back, but forgot about it, but with bonnet up, seats up, etc.... as soon as you turn the key all hell lets loose....

I think it's a 2 wire sensor, so could it be wired to default on instead of off, like a safety circuit, in case of engine overheat?


John

[brorabongo]

Picture No.2 I would say.

I won't pretend to understand how it works, all I know is that if the circuit is "open" then the rad fans come to life. You can test this by unpluging the sensor. (there is a connection just below the earthing plate) This could be done as quick test, to see if the fans themselves are working ok.

I just noticed that Oggy's fans would come on as soon as the key was turned. I found out with help on here, where the switch is, and on inspection found the sensor to be as my above post's picture. Now replaced, all seems well.

[Grahame at work]

Hi John,

The two wire sensor tells the ECU the temperature of the coolant and is a thermistor that reduces in resistance as the temperature increases. The ECU can tell if it is not connected in which case it turns the fans on all the time.

The other sensor, top front of the head is a single wire sensor for the dash gauge.

Simon,

I have been running experiments on the cooling system by monitoring the temperature of various hoses and monitoring the voltage developed across this ECU coolant temperature sensor. This is to try and develop a decent theory of operation for the cooling system.
I could do with getting hold of a spare sensor to run a calibration on it as the workshop manual only gives me a couple of calibration points. Is there any chance of me getting hold of those sensors you offered to John if he doesn't take up your offer?
I can return them to you (or anyone else) when I have run a calibration on them by connecting them into my system and sitting them in a pan of hot water.

Regards Grahame

[bongoing-mad-simon]

hi john, its on its way.......

[bongoing-mad-simon]

Simon,

I have been running experiments on the cooling system by monitoring the temperature of various hoses and monitoring the voltage developed across this ECU coolant temperature sensor. This is to try and develop a decent theory of operation for the cooling system.
I could do with getting hold of a spare sensor to run a calibration on it as the workshop manual only gives me a couple of calibration points. Is there any chance of me getting hold of those sensors you offered to John if he doesn't take up your offer?
I can return them to you (or anyone else) when I have run a calibration on them by connecting them into my system and sitting them in a pan of hot water.

Regards Grahame

sorry Grahame if i had any more they'd be yours ..................

[sajseven]

A stupid question... is the air-con/heater unit switched completely off? This turns the fans on on ours if you turn it on...

[Rhod]

Sajseven - are you saying that your heater controls turns your engine cooling fans on