Got a dilemma, there are 2 blue temperature sensors showing for the same position on the citroen service website (number 8 on the diagram):
One says 110 degrees and the other 118 degrees. I don't suppose anyone knows which is the correct part for this engine? It's the XUD9TE engine in a 1998 Xantia 1.9TD. I used the VIN for part searching yet still have these two show up with no indication which is correct.
Have asked my dad to check it over for any writing, otherwise not sure what to do as don't want to get it wrong.
Out of interest, don't suppose anyone knows what function thermistor 11 on the diagram has? From what I've gleaned, 8 is the temp sensor for the ECU and 9 is for the Bitron to control radiator fans, etc.
Thanks for all the advice. I was working late-shift today and unable to advise them. Came home to find they'd telephoned the nearest Citroen stealer and asked them to order the blue temp sensor, leaving it to them to supply the correct one... Hope they know which it should be.
My dad removed the original and it only had this writing on it: 21A8 and 336401 and 03. So nothing obviously helpful. I'll let you know which one Citroen supply as it's being collected tomorrow.
I wonder why, even when using the VIN on the service website, it shows both, and which is used where and why.
After thinking about the fast-idle and air-con not running at idle problems, as posted on this forum, having returned back to the UK, I suddenly realised the implications of a faulty thermistor, primarily the blue one as I'd read it supplied the ECU with temperature information. Got my dad to test the blue one - it's open-circuit. Assuming it's NTC, which it should be, that means it's telling the ECU that the engine is always very cold. I also asked him to test the brown and green ones too, the brown one (9) read 2.45 KOhms, and the green one read 436 Ohms. Engine was still warm having been used earlier.
Should the new sensor cure the problems mentioned in the other topics I started while in Spain, I'll update them so future searches for similar problems don't lead to the annoying lack of conclusion.
For anyone finding this with a search, the issues generally are:
- Slow to start when cold, giving a bit of a 'kick' before catching.
- Hard to start when hot, much worse than when cold.
- More sluggish than I expected after having owned a 1.9TD myself.
- Fast-idle always on after replacing open-circuit fast-idle solenoid (blue one).
- Air-con not working at idle, only kicking in when driving - compressor clutch held off by relay.
Got a dilemma, there are 2 blue temperature sensors showing for the same position on the citroen service website (number 8 on the diagram):
One says 110 degrees and the other 118 degrees. I don't suppose anyone knows which is the correct part for this engine? It's the XUD9TE engine in a 1998 Xantia 1.9TD. I used the VIN for part searching yet still have these two show up with no indication which is correct.
Thanks
Number 11-green sensor...this is the ECO COOLANT TEMP SENSOR.
Then on the other side of the filter, the one on the left is a thermistor that supplies the signal for the DASH TEMP GAUGE.
The one on the right is linked to the fans and probably the aircon.
New blue sensor was got today, and it's the 118 degree type which the spares chap said was the right one for this car. However, it also reads open-circuit and has made no difference to the car.
It's been tested using a multimeter in the 20 MegOhm range. However, disconnecting it does indeed affect the temp gauge in the car, as said in the previous reply (thanks crossy), so that confirms that. Odd it works the gauge but reads open on 20 megohm.
Back to square one by the looks of things, as the green one, which must be for the ECU, is reading okay. Don't know what it should be at different temps but read around 436 ohms when engine warm the other day.
JamesQB wrote:New blue sensor was got today, and it's the 118 degree type which the spares chap said was the right one for this car. However, it also reads open-circuit and has made no difference
That's a kick in the teeth! Does it mean you have (or were given) wrong specification data?
I'd be seeing what it does at 118°C+ before condemning it.
Did you try the resistance in both directions, and to ground? What if it also had a cap or diode in there? Not suggesting it does, but looking at ways it might skew a meter reading.
I am assuming the sensor also uses its body to ground. Perhaps resistance of one terminal to earth changes with temp, and at 118° the secondary contacts trip to a dead short?
Mike, it was more that scouring the net for the tiny bits of information I could find seemed to indicate that the blue sensor was the ECU one. I have no specs to go by for any of the sensors because I can find no information on the XUD9TE engine whatsoever. My 1993-1998 Xantia manual doesn't include it and I can find nothing at all on the internet. I have both autodata and vivid workshop but they ignore the engine management side of things completely. I've spent hours searching the net for service manuals, workshop manuals, anything at all, but this engine seems to be obscure when it comes to interest in it and documents for it.
I don't know what, if anything, it should do at 118C. I had wondered if it was a thermostatic switch and that's why there were two available, one made to go at 110 and one at 118 degrees. I think your idea of both pins reading to ground, one being a thermistor and the other a thermostatic switch is very good and will ask my dad to check that out. I have no reason to think old one is faulty, as gauge was working fine and car rarely gets past 70 degrees.
Due to lack of available info on this engine, I think it's a case of my parents mortgaging the house and letting Citroen change 20 parts on it. At least Citroen can connect a Lexia (if the Spanish outfits even bother with them) to it and see what's happening. I'm working blind.
For search purposes since I cannot find the info anywhere else... the blue sensor, Citroen part number 0242 85 (024285) is actually exactly as addo said it might be. Here is the information as we have found it for all three sensors:
BLUE: Temperature gauge sensor and thermostatic switch in one unit, which delivers temperature information to the dashboard coolant temperature gauge as well as having a thermostatic switch which goes from open-circuit condition to short-circuit condition when coolant temperature reaches stated operating temperature of sensor (110 or 118°C). Citroen part number 0242 85 is the 118°C type, and 1338 09 is the 110°C type. Our 1998 Xantia 1.9TD with XUD9TE engine uses the 118°C type according to Citroen dealer.
Measured open-circuit (infinity) between the two pins at all times.
From one of the pins to the brass body of the sensor: With engine around 70°C it measured: 320 Ohms. With engine cold it measured: 1.7 Kilohms.
This is the temperature gauge sensor and is a thermistor.
From the other pin to the brass body of the sensor: With engine hot or cold, it measured: open-circuit.
It should go short-circuit if coolant temperature reaches designated limit of sensor.
BROWN: Bitron Sensor, presumably for determining activation of radiator fans. Thermistor is connected between the 2 pins. No connection to metal body of sensor.
With engine around 70°C it measured: 2.76 Kilohms. With engine cold it measured: 1.48 Kilohms.
GREEN: Coolant temperature sensor which delivers temperature information to the ECU. Thermistor is connected between the 2 pins. No connection to metal body of sensor.
With engine around 70°C it measured: 247 Ohms. With engine cold it measured: 1.7 Kilohms.
The brown Bitron sensor seems to be a PTC thermistor. The others seem to be NTC thermistors. Air temps were around 25-30°C.
Last edited by JamesQB on 07 Jul 2009, 01:11, edited 1 time in total.
That might help...same engine. So same electrics too.
I dont think the eng coolant sensor is giving the correct readings.
THESE are the figures you should get....PM me your email, I have a couiple of things that may help.
10°C 3530-4100 ohms
20°C 2350-2670
40°C 1085-1230
60°C 540-615
80°C 292-362
100°C 165-190
