Xantia Engine Temperature Sensing and Bitron Unit
Recently had the experience of overheating my 1994 2.0i Xantia due to loss of coolant fluid. Although the temperature gauge is working accurately against the thermostat value, the alarm light in the gauge did not trigger until nearly at 120degreesC. I noticed the light come on (it was twilight) and immediately switched off.
Since then, there is a pressure residue in the cooling system, with gas escaping when the reservoir cap is released even when the engine is fully cold. My interpretation is that a pinhole leak has developed in the head gasket between a combustion chamber and the coolant jacket. The engine oil is unaffected, and the engine runs and pulls as normal (apart from atrocious starting), and the coolant slowly disappears.
This leak indicates that the temperature sensing system on this Xantia failed to protect against warping of the alloy head due to loss of coolant.
Looking for the engine temperature sensor, I do not locate a temperature sensor on the 3 visible sides of the head, but find a possible candidate adjoining the engine oil dipstick. But if this really is the engine temperature sensor, then all Xantias of the same design would be susceptible to expensive engine problems as a result of coolant loss, because as the water drains from the head, the head will be the first engine component that will overheat.
In the head is where the engine temperature sensor should be, so that temperature is monitored at the point which will be first to overheat.
Then there is the matter of the warning light not coming on until normal operating temperature (88 to 93 DegreesC) was exceeded by an extremely large margin. My instinct is that there was some fault in the apparatus which detects and triggers an overtemperature warning light, because with a 20psi relief cap I would anticipate a designed triggering temperature of about 105 degreesC. So, why did my warning light not trigger until 15 degrees above that ?
Is a faulty Bitron Unit a candidate for this discrepancy ?
Is the Bitron Unit a simple passive device, or does it perform complex signal-conditioning functions ?
Is the Bitron Unit (with its reputation for unreliability) serving some uniquely useful purpose, or can it be bypassed with reliable commonplace components ?
Where is the engine temperature sensor ?
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Xantia Engine Temperature Sensing and Bitron Unit
Moderator: RichardW
Peter -
There MUST be at least 2 separate sensors in the head -
One for the ECU - 2pole connector piece.
One for the overtemp warning lamp - or temp gauge with build-in electronics for the warning lamp - 1pole connector.
I have yet to see these 2 sensors combined into one unit.
I can only agree that any coolant temp sensors fitted in the block would be insane - and this is NOT the case on Citroen engines.
The sensor you found near the dipstick is for any oil gauge - being level or pressure.
As you know from your BX - there are 2 each 1pole sensors for the warning lamps - one of these would be extinct in favor of a 2pole sensor for later injection fitted BX'es.
They should be found near the thermostat housing - i.e. at flywheel end of top - known to have moved around a bit on various generation Citroen engines.
BTW your radiator fitted coolant level warning did not work ?
PS : You're aware that recently the Czek site added info on the Xantia aircon ? :
http://citroeny.cz/servis/xantiaser/klima/klima.htm
There MUST be at least 2 separate sensors in the head -
One for the ECU - 2pole connector piece.
One for the overtemp warning lamp - or temp gauge with build-in electronics for the warning lamp - 1pole connector.
I have yet to see these 2 sensors combined into one unit.
I can only agree that any coolant temp sensors fitted in the block would be insane - and this is NOT the case on Citroen engines.
The sensor you found near the dipstick is for any oil gauge - being level or pressure.
As you know from your BX - there are 2 each 1pole sensors for the warning lamps - one of these would be extinct in favor of a 2pole sensor for later injection fitted BX'es.
They should be found near the thermostat housing - i.e. at flywheel end of top - known to have moved around a bit on various generation Citroen engines.
BTW your radiator fitted coolant level warning did not work ?
PS : You're aware that recently the Czek site added info on the Xantia aircon ? :
http://citroeny.cz/servis/xantiaser/klima/klima.htm
"BTW your radiator fitted coolant level warning did not work ?"
Anders, I don't think my 96 XTD comes with the device. Is it the sensor on the cap of the coolant spare tank? I don't have the sensor, just the cap but I can buy a sensor and the wiring is in place. Where does the warning light show up? My manual doesn't indicate where the warning turns up either. Is it possible to install it? Thanks.
Anders, I don't think my 96 XTD comes with the device. Is it the sensor on the cap of the coolant spare tank? I don't have the sensor, just the cap but I can buy a sensor and the wiring is in place. Where does the warning light show up? My manual doesn't indicate where the warning turns up either. Is it possible to install it? Thanks.
I checked with Haynes Xantia electric schematics -
According to the legend for the coolant temperature/level warning circuit - there is no sensor fitted in the radiator (other than the fan thermoswitch).
Instead you have near the thermostat housing a combination sensor fitted : a level warning switch & temperature sensor for the gauge.
<font color="red"><i>This is in fact a 2pole sensor.</i></font id="red">
- not to be confused with the ECU engine temp sensor.
On turbo diesels an extra separate over-temperature warning switch is fitted - but where this is located is not clear from the legend.
I don't know how to interprete "level" from this legend [:o)]
It could be "warning level" for the temperature - or low coolant level.
According to the legend for the coolant temperature/level warning circuit - there is no sensor fitted in the radiator (other than the fan thermoswitch).
Instead you have near the thermostat housing a combination sensor fitted : a level warning switch & temperature sensor for the gauge.
<font color="red"><i>This is in fact a 2pole sensor.</i></font id="red">
- not to be confused with the ECU engine temp sensor.
On turbo diesels an extra separate over-temperature warning switch is fitted - but where this is located is not clear from the legend.
I don't know how to interprete "level" from this legend [:o)]
It could be "warning level" for the temperature - or low coolant level.
Thanks Anders. I thought there could be a coolant level sensor next to the coolant expansion tank filler cap in newer cars. Saw it in a newer XTD but the wiring was not plugged in. The mechanic said the wiring can't be plugged in as the car will show the stop sign. Was confused whether its meant to be a coolant level sensor at all.
Re: Xantia Engine Temperature Sensing and Bitron Unit
I measured my ECU (green) coolant temp. sensor with ohm meter.
@ 21 °C the resistance was 2450 ohms.
Citroen says it should be 2500 ohms @ 20 °C.
So, is my CTS faulty? Should i replace it?
@ 21 °C the resistance was 2450 ohms.
Citroen says it should be 2500 ohms @ 20 °C.
So, is my CTS faulty? Should i replace it?
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Re: Xantia Engine Temperature Sensing and Bitron Unit
You only have a 2% discrepancy, which may be partly explained by not measuring at 20°C, so I don't think you have a problem there.
BTW, you have replied to a topic which is more than 10 years old!
BTW, you have replied to a topic which is more than 10 years old!
Re: Xantia Engine Temperature Sensing and Bitron Unit
No, that's close enough.
About 2000 Ohms when cold and 3500 Ohms with a hot engine.
About 2000 Ohms when cold and 3500 Ohms with a hot engine.
2002 C5 2.0i AL4 230,000 km 76372389
Re: Xantia Engine Temperature Sensing and Bitron Unit
Because i didn't want to create a thread for just a simple question.BTW, you have replied to a topic which is more than 10 years old!
I also measured the instrument cluster coolant temp. sensor. The blue one that has only one terminal.
@ 21 °C it's resistance was 2863 ohms.
Is it faulty?
They are NTC type sensors. When engine gets hot, their resistances go lower.About 2000 Ohms when cold and 3500 Ohms with a hot engine.
@ 20 °C = 2500 ohms
@ 90 °C = 230 ohms