Hi,
I am hoping someone can offer some advise with a cooling problem on a 98 (new shape) Xantia 1.9TD with aircon.
As a result of a recent overheating problem when towing i sought some advice from a local garage on the possible problem and as a result discovered the cooling fans are not working as they should.
With the air con on the fans both operate at low speed. When the engine is hot both cooling fans cycle on and off at low speed (with aircon off).
The problem seems to be that when the engine is exceptionally hot the cooling fans will not operate at high speed.
The local dealer discovered this by removing the bitron sensor wire (which i understand should make the fans operate at high speed), this was done with the air con on and the fans carried on operating at low speed.
I have spent the evening experimenting with the relays between the fans and am more confused than when i started! There are two green and one black relay. With the engine and aircon on, removing the black or one of the green relays seems to make the fans stop. Removing the other green (top right) relay does nothing, however shorting the switched terminals of said relay makes the right fan operate fast whilst the left one stops (v confused!) Finally i've been searching for the bitron unit (as it was suggested this could be at fault). I have removed both front headlamps and the only thing I can see that looks like it is on the drivers side immediatly behind the headlamp. It has a large connector on the wing side and on the engine side a white block with something that looks like a black connector in it. Have i found it? If not any suggestions where to look.
Any help would be VERY gratefully recieved.
Simon Howard
Xantia Cooling Fans
Moderator: RichardW
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simonhoward34
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- Location: United Kingdom
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simonhoward34
- Posts: 4
- Joined: 31 Jul 2003, 02:18
- Location: United Kingdom
- My Cars:
On the day the car overheated the temp went up past 120 degrees c and the stop light came on, I checked the fans and they were both running but at low speed.
My understanding is that removing the connector from the biron sensor should make the fans default to fast speed and this does not appear to happen.
Insidentally i have located the bitron unit and am contmplating ordering a replacement to see if this is at fault.
Simon
My understanding is that removing the connector from the biron sensor should make the fans default to fast speed and this does not appear to happen.
Insidentally i have located the bitron unit and am contmplating ordering a replacement to see if this is at fault.
Simon
Simon,
The interconnections and interdependencies of the radiator cooling fans and the aircon in Xantias of either fuel is fiendishly complex and quite capable of producing all the anomalies you describe - and a completely different set for my petrol 96 estate.
Whilst I can unfortunately offer no helpful diagnosis, I can describe my own 'patient's' symptoms in the hope that some elevated intelligence out there in ForumLand might put these two chunks of information together and offer some wisdom of use to us both.
First off - the aircon illuminated on/off switch on the dash doesn't work and hasn't worked since day one of my ownership. For four years the cabin *climate control* worked sweetly so I never gave the switch more than a passing glance and the odd tap to see if the blue light might come on - it never did. However in winter the cabin was warm and in summer, nice and chilly, so I left well alone, knowing that the 'auto' setting in the slider array was doing its stuff, maintaining 22c whatever the weather.
Great system which gave me quiet satisfaction over the years.
Until a year ago.
Whilst idling at traffic lights a couple of miles from home in ordinary temperate weather, I noticed a huge increase in under bonnet noise and an electrical surge sufficient to pull down the engine revs by half. The howling gale under the bonnet confirmed that both rad fans were operating on maximum.
The 'low speed running' of the dual radiator cooling fans does not happen at all for me - would that it did - all I get, with cabin temperature control set to '22' and fan slider to 'auto' is the howling tornado under the bonnet of maximum radfans after a few minutes of running and engine temp of 60 or 70c. This happens winter or summer, and, the Haynes manual being its usual inscrutable self (i.e. useless), I have had to develop two workarounds that are revealing in their effect and so will be described fully.
Ludicrous overcooling being the problem, I removed the underbonnet fuses #3(30A) and #5(5A)- curiously, just removing the big 30A on its own doesn't stop the fans' cutting in, but both does.
With this setting, the heater works and the natural convection forces of driving normally keep the engine within temperature operating limits - obviously this wouldn't work in a major stop-start traffic crawl, but this has only been a major problem once when temperature rose to 120c (!) and I had to jump out and put the fuses back - the maximum gale force blast quickly extinguished the STOP light and off I drove with no ill effects.
This might be considered an extreme solution, but I use it often in summer, as it is the only way to enjoy cabin cooling without aircraft-carrier-like sonic accompanimemt.
In winter, and here is the clue to interdependence mentioned above, I replace the fuses, and with the cabin auto/off/max slider set at 'auto' the heater works normally and the usual under-bonnet racket cuts in somewhat later and not at all whilst driving at a steady cruising speed, until slowing for lights or roadworks when the wind tunnel returns...HOWEVER, moving the fan slider to 'off' stops the under bonnet fans in their tracks. More testing revealed that they would remain stopped even in a controlled extended idle up to 100c+ coolant temp, at which point merely moving the in-cabin fan slider back to 'auto' would immediately start up the maximum rad fans.
When pressed, the Haynes manual will reluctantly mumble something like "...bitron...CPU...Citroen Dealer...special equipment required..." the translation? "Everything depends on everything, you'll never figure it out, so we haven't bothered on your behalf, thanks for the money".
Thregwort, Essex UK.
The interconnections and interdependencies of the radiator cooling fans and the aircon in Xantias of either fuel is fiendishly complex and quite capable of producing all the anomalies you describe - and a completely different set for my petrol 96 estate.
Whilst I can unfortunately offer no helpful diagnosis, I can describe my own 'patient's' symptoms in the hope that some elevated intelligence out there in ForumLand might put these two chunks of information together and offer some wisdom of use to us both.
First off - the aircon illuminated on/off switch on the dash doesn't work and hasn't worked since day one of my ownership. For four years the cabin *climate control* worked sweetly so I never gave the switch more than a passing glance and the odd tap to see if the blue light might come on - it never did. However in winter the cabin was warm and in summer, nice and chilly, so I left well alone, knowing that the 'auto' setting in the slider array was doing its stuff, maintaining 22c whatever the weather.
Great system which gave me quiet satisfaction over the years.
Until a year ago.
Whilst idling at traffic lights a couple of miles from home in ordinary temperate weather, I noticed a huge increase in under bonnet noise and an electrical surge sufficient to pull down the engine revs by half. The howling gale under the bonnet confirmed that both rad fans were operating on maximum.
The 'low speed running' of the dual radiator cooling fans does not happen at all for me - would that it did - all I get, with cabin temperature control set to '22' and fan slider to 'auto' is the howling tornado under the bonnet of maximum radfans after a few minutes of running and engine temp of 60 or 70c. This happens winter or summer, and, the Haynes manual being its usual inscrutable self (i.e. useless), I have had to develop two workarounds that are revealing in their effect and so will be described fully.
Ludicrous overcooling being the problem, I removed the underbonnet fuses #3(30A) and #5(5A)- curiously, just removing the big 30A on its own doesn't stop the fans' cutting in, but both does.
With this setting, the heater works and the natural convection forces of driving normally keep the engine within temperature operating limits - obviously this wouldn't work in a major stop-start traffic crawl, but this has only been a major problem once when temperature rose to 120c (!) and I had to jump out and put the fuses back - the maximum gale force blast quickly extinguished the STOP light and off I drove with no ill effects.
This might be considered an extreme solution, but I use it often in summer, as it is the only way to enjoy cabin cooling without aircraft-carrier-like sonic accompanimemt.
In winter, and here is the clue to interdependence mentioned above, I replace the fuses, and with the cabin auto/off/max slider set at 'auto' the heater works normally and the usual under-bonnet racket cuts in somewhat later and not at all whilst driving at a steady cruising speed, until slowing for lights or roadworks when the wind tunnel returns...HOWEVER, moving the fan slider to 'off' stops the under bonnet fans in their tracks. More testing revealed that they would remain stopped even in a controlled extended idle up to 100c+ coolant temp, at which point merely moving the in-cabin fan slider back to 'auto' would immediately start up the maximum rad fans.
When pressed, the Haynes manual will reluctantly mumble something like "...bitron...CPU...Citroen Dealer...special equipment required..." the translation? "Everything depends on everything, you'll never figure it out, so we haven't bothered on your behalf, thanks for the money".
Thregwort, Essex UK.
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Dave Burns
- Posts: 1915
- Joined: 14 May 2001, 05:30
- Location: United Kingdom
- My Cars:
- x 2
Hmmm........yep same here, noticed the fans kept bursting into high speed when aircon on and engine at normal temp a few weeks ago, left car ticking over while at bottle bank and heard fans go into overtime, thought I'd better have a look what the temp was and it was normal.
This must be purely a function of the aircon then, perhaps some temperature sensor on the condenser in front of intercooler, didn't do it while car was moving, only stationary.
Had the temp gauge highest its ever been on any of my diesels that day about half hour after noticing the fan activity, didn't think fans had cut it but can't be sure, was going up a steep hill towing my trailer and with three adults in car (by that time had aircon off and all windows open so plenty of noise about) so it had its work cut out in the scorching heat of that day.
I can pull bitron temp sensor connector on stat housing off and fans kick in at high speed instantly so wasn't too worried.
Will keep a close eye on it from now on.
Dave
This must be purely a function of the aircon then, perhaps some temperature sensor on the condenser in front of intercooler, didn't do it while car was moving, only stationary.
Had the temp gauge highest its ever been on any of my diesels that day about half hour after noticing the fan activity, didn't think fans had cut it but can't be sure, was going up a steep hill towing my trailer and with three adults in car (by that time had aircon off and all windows open so plenty of noise about) so it had its work cut out in the scorching heat of that day.
I can pull bitron temp sensor connector on stat housing off and fans kick in at high speed instantly so wasn't too worried.
Will keep a close eye on it from now on.
Dave
Dave,
That's reassuring, [to hear of a nearly identical sufferer] if we can run this problem to earth it may not be one of those *dealer only* replace-everything-at-their-prices type scenario.
There must be others out there...let's keep this thread active and see what our combined knowledge will bring to light.
Thregwort, Essex UK.
That's reassuring, [to hear of a nearly identical sufferer] if we can run this problem to earth it may not be one of those *dealer only* replace-everything-at-their-prices type scenario.
There must be others out there...let's keep this thread active and see what our combined knowledge will bring to light.
Thregwort, Essex UK.
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Dave Burns
- Posts: 1915
- Joined: 14 May 2001, 05:30
- Location: United Kingdom
- My Cars:
- x 2
Bit more on the subject, tested resistance of bitron sensor today, 1.8k cold and 2.7k at normal running temp, anyone concur with those measurements, wonder what resistance the fans kick in at, should be able to find it with a suitable pot, can then stuff sensor in water and bring to boil, see if required resistance obtained before boiling.
Why don't A/s sell these, they sell the bitron aircon ecu so why not its sender?.
Dave
Why don't A/s sell these, they sell the bitron aircon ecu so why not its sender?.
Dave
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Jon
All,
Ah, the bitron sensor, that Holy Grail so fleetingly (yet alluringly) referred to by Haynes before moving on to something altogether more interesting like "how to put a bit of cloth over the radiator cap if removing when hot".
If only simonhoward34 had been paying more attention when "the local dealer discovered this by removing the bitron sensor wire" as later in his post he states that he has ripped most of the front of his car off looking for it!! (sorry si!:-)
Finally, help is at hand...c'mon Dave, tell us where it is, pleeeeze!!!
Thregwort, Essex UK.
Ah, the bitron sensor, that Holy Grail so fleetingly (yet alluringly) referred to by Haynes before moving on to something altogether more interesting like "how to put a bit of cloth over the radiator cap if removing when hot".
If only simonhoward34 had been paying more attention when "the local dealer discovered this by removing the bitron sensor wire" as later in his post he states that he has ripped most of the front of his car off looking for it!! (sorry si!:-)
Finally, help is at hand...c'mon Dave, tell us where it is, pleeeeze!!!
Thregwort, Essex UK.
Thanks wheeler,
I think the reason only a few forum posters can find this item is due to, and I quote from Haynes - "On some models, access to the switch is very poor, and other components may need to be removed before the sender unit can be reached". Haynes agrees however, that a brown wiring connector is the identifying characteristic.
So we know where it is - and it seems highly likely that replacing it will restore normality to the aircon/cooling fan interdependence - but AndySpares do not appear to stock the item!
I fear the *Main Dealer* is getting closer...anyone bought elsewhere at reasonable prices?
Thregwort, Essex UK.
I think the reason only a few forum posters can find this item is due to, and I quote from Haynes - "On some models, access to the switch is very poor, and other components may need to be removed before the sender unit can be reached". Haynes agrees however, that a brown wiring connector is the identifying characteristic.
So we know where it is - and it seems highly likely that replacing it will restore normality to the aircon/cooling fan interdependence - but AndySpares do not appear to stock the item!
I fear the *Main Dealer* is getting closer...anyone bought elsewhere at reasonable prices?
Thregwort, Essex UK.
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simonhoward34
- Posts: 4
- Joined: 31 Jul 2003, 02:18
- Location: United Kingdom
- My Cars:
All,
For info i have solved the problem of fans not working at high speed. After finding the BITRON CONTROL UNIT (not bitron sender unit, i knew where that was by observing the dealers investigations!!) I swapped said item for new one only to find the same problem occurred. Fortunatly, further ivestigation showed that the diagram in the Haynes manual accuratly represents the circuit in my Xantia and i managed to determine that the system works as follows (might be of use to others).
A positive 12v feed is present to the three fan relays irrespective of whether fans are required. When slow speed fans are required the bitron controller switches the negative side of the the green bottom left coil to earth (i.e. 12v across relay) this puts both fans in series (6v across each). When high speed fans are required the negative of both other relays (one black one green) are shorted to earth by bitron control unit and relays energise. This has the effect of putting 12v across each fan (i.e. high speed)
In my case i eventually discovered the connection from pin 2 of the black relay (referred to as series relay in haynes manual) to pin 10 of the bitron control (which should be a straight link) was broken somewhere behind the fan assembly. Have replaced said wire and all is now fine. Incidentally i have a resistance box and have substituted this for the bitron sender unit. On mine the fans kick in on slow speed at 2.8K ohms and at high speed at 3.1k ohms.
Cheers
Simon
For info i have solved the problem of fans not working at high speed. After finding the BITRON CONTROL UNIT (not bitron sender unit, i knew where that was by observing the dealers investigations!!) I swapped said item for new one only to find the same problem occurred. Fortunatly, further ivestigation showed that the diagram in the Haynes manual accuratly represents the circuit in my Xantia and i managed to determine that the system works as follows (might be of use to others).
A positive 12v feed is present to the three fan relays irrespective of whether fans are required. When slow speed fans are required the bitron controller switches the negative side of the the green bottom left coil to earth (i.e. 12v across relay) this puts both fans in series (6v across each). When high speed fans are required the negative of both other relays (one black one green) are shorted to earth by bitron control unit and relays energise. This has the effect of putting 12v across each fan (i.e. high speed)
In my case i eventually discovered the connection from pin 2 of the black relay (referred to as series relay in haynes manual) to pin 10 of the bitron control (which should be a straight link) was broken somewhere behind the fan assembly. Have replaced said wire and all is now fine. Incidentally i have a resistance box and have substituted this for the bitron sender unit. On mine the fans kick in on slow speed at 2.8K ohms and at high speed at 3.1k ohms.
Cheers
Simon
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Dave Burns
- Posts: 1915
- Joined: 14 May 2001, 05:30
- Location: United Kingdom
- My Cars:
- x 2
Very good info there Simon thanks, I'm surprised to see that it will only take a jump of only 100ohms further resistance to kick the fans in at low speed, but another 300ohms to get them going at high speed, especialy given the amount of change in resistance from cold to normal running temp, can you (and others if you have a good meter) measure the resistance of the sender at cold and normal running temp, if so it might help towards finding the norm. for this device.
Jon thanks, yes thats the position of it right enough, but both sender and connector are very definately brown.
I'm not necessarily saying there is anything wrong with the one on my car, just trying to make sure there isn't, cos' we all know the outcome of over heating these lumps, just thought it to be a good idea to have a few on the shelf.
Dave
p.s Jon, sending a mail just incase you miss it.
Jon thanks, yes thats the position of it right enough, but both sender and connector are very definately brown.
I'm not necessarily saying there is anything wrong with the one on my car, just trying to make sure there isn't, cos' we all know the outcome of over heating these lumps, just thought it to be a good idea to have a few on the shelf.
Dave
p.s Jon, sending a mail just incase you miss it.