xantia stop light

KevMayer · Post by **KevMayer** » 27 Dec 2005, 22:31

Another thought -

Foot Brake brings on the light and you have passenger door central locking problems. Could it be a bad earth problem ?

Mandrake · Post by **Mandrake** » 27 Dec 2005, 22:43

KevMayer wrote:The BITRON controls the radiator cooling fans and some aircon giggerypokery. If it were this problem then you'd get another symptom of the radiator fans running on high speed.

Hi Kev,

When hot mine occasionally switches to high speed fans for only a second or two then back, then back to high and back a few times at random. I also have a problem with the air conditioning clutch not wanting to operate sometimes at random. (Usually on a very hot day

)

Could these both be the infamous Bitron sensor to blame ? Can someone tell me exactly where it is on a 2 litre 8 valve petrol engine ?

Regards,
Simon

Richard Gallagher · Post by **Richard Gallagher** » 28 Dec 2005, 09:24

The Bitron sensor is tucked right underneath the N/S/F headlight and is a right swine to gain access to.
You'll need to remove the headlight and quite possibly the bumper to get it out as a panel runs right across the top of it.

The cause of the fans switching briefly to fast and the aircon compressor not engaging on hot days is more than likely due to a problem with excess pressure build up within the aircon system. This in turn could be down to too much gas being put into the system when last recharged. Does the engine briefly falter/stall when this happens? If so then its a good indicator of the above fault.

Getting back to the original topic, the fact that the stop light illuminates whenever there is a demand from the hydraulic system (ie steering/brakes, bumpy road/suspension, stop light takes ages to go out from start up) suggests to me that the pressure within the hydraulic system is too low.

Personally I'd start with replacing the accumulator sphere (£20) and maybe a flush with Hydraflush (£15) as a relatively inexpensive start as a cure. It may however turn out to be that the pump is on the way out.

If it's an electrical earthing problem then operate numerous electrical items and look for 'unusual' happenings such as dim lights, clicking noises from relays etc. Also get hold of a voltage meter and compare the voltage readings on various circuits around the car.

Mandrake · Post by **Mandrake** » 28 Dec 2005, 11:06

Richard Gallagher wrote:The Bitron sensor is tucked right underneath the N/S/F headlight and is a right swine to gain access to.

N/S/F ??? What is that ? Left or right ?

You'll need to remove the headlight and quite possibly the bumper to get it out as a panel runs right across the top of it.

Yikes... is it large ? Or just well hidden ?

The cause of the fans switching briefly to fast and the aircon compressor not engaging on hot days is more than likely due to a problem with excess pressure build up within the aircon system. This in turn could be down to too much gas being put into the system when last recharged. Does the engine briefly falter/stall when this happens? If so then its a good indicator of the above fault.

Fascinating... so the pressure switch on the bottle will also register too MUCH pressure and prevent the aircon enabling ? I always thought the switch was there to prevent it operating with not enough pressure...

Funny thing is there seems to be no correlation between ambient temperature and whether it will work or not, it seems almost entirely random, except I notice that if it decides not to work initially sometimes after a few minute driving it will work, but often not.

As for the fans coming onto high speed - this happens (and only very rarely) with the air conditioning off, typically when the car has been idling for a long period of time while I've been fiddling with the suspension height for example, it will burst up to the high fan speed for a second or two at a time, then back to normal, with the air conditioning turned off...

Regards,
Simon

Clogzz · Post by **Clogzz** » 28 Dec 2005, 11:11

Mandrake wrote:Can someone tell me exactly where it is on a 2 litre 8 valve petrol engine ?

Hello Simon,

Picture showing where the Bitron is on the petrol cars.

This Bitron fault is my little favourite.
It causes the STOP light and small light inside the temperature gauge to come on at the same time, and also causes the fans to go to the high speed, but not always coinciding with the lighting of the warning lamps.

The pins of the Bitron are tinned with solder, and they need a good scrape.
I scraped them with the rough end of a broken piece of metals hacksaw blade, then swept out the scraps of solder.
It's been good since, and I know that it's fixed.

I had tried in the past to clean them with a little blunt screwdriver, and then squirted them with WD40, but that's only been good for 3 days back then.

This fault also causes the fans to turn on at the low speed after stopping the engine after short trips when the engine doesn't even have the time to reach normal operating temperature.

On the diesels, the Bitron lives behind the passenger's side headlight.
Because of that, it has a long wire lenght, and an intermediate plug/connector that has intermittencies that cause the same fault.
There is a modification that consists of hard-wiring the intermediate connector, and changing the triggering of the warning lamps:

http://xu10j4r.free.fr/xantia/notexantia.pdf 220KB

Bitron plug on diesels:

Cooling fan electrics:

http://www.frenchcarforum.co.uk/forum/v ... hp?t=17012

Richard Gallagher · Post by **Richard Gallagher** » 28 Dec 2005, 11:53

Simon, the Bitron cooling fan control box is normally located directly under the nearside (kerbside on RHD cars or the left as you look forward from the drivers seat. i.e. just in front of the battery) headlight.

Quite what the box shown on Clogzz pic is I'm not sure, but be mindful that "Bitron" is a trade name, so the fact that you may discover a box with Bitron written thereon does not mean its the one that controls the cooling fans (I made that mistake some time ago). The size of the box is roughly that of a "double length" matchbox with the connecting socket on one end.

From the sound of your description it appears as if your car is not suffering from "overgassing", but an intermittant connection on the aircon system such as the Bitron contol box. The fans switching onto high speed when left iding as you describe sounds pretty normal to me.

Clogzz · Post by **Clogzz** » 28 Dec 2005, 12:20

Richard Gallagher wrote:Quite what the box shown on Clogzz pic is I'm not sure

It looks like the Bitron to control the cooling fans and air conditioning is inside the fuse box on all petrol cars.
Never seen a diesel here, but I understand that the Bitron is behind the passenger's side headlight on them.
I've added to my story above about that.

Richard Gallagher · Post by **Richard Gallagher** » 28 Dec 2005, 16:28

Just to confuse matters I have found the Bitron control box for the fans/aircon under the headlight on a 97 2.0 16V petrol, as per the second photo.

Diesels also have a Bitron box in the fusebox, but I believe that it does something else other than control the fans/aircon.

It's this box that I got confused with as per my earlier post.

JohnT · Post by **JohnT** » 28 Dec 2005, 16:44

One of the cuff as I do not have a handbook to check.....what lights up if the front disc pads are worn down and earthing the circuit???

AndersDK · Post by **AndersDK** » 28 Dec 2005, 16:51

Donno whats up with the board server right now.
Just deleted a number of unwanted postings from Richard G - and the last triplicate postings from JohnT.
(Almost lost my breath catching up

)

Richard Gallagher · Post by **Richard Gallagher** » 28 Dec 2005, 17:19

AndersDK wrote:Donno whats up with the board server right now.
Just deleted a number of unwanted postings from Richard G - and the last triplicate postings from JohnT.
(Almost lost my breath catching up )

Thanks Anders.

The pad warning light IIRC is a yellow light with a circle on it.

Mandrake · Post by **Mandrake** » 28 Dec 2005, 19:44

Clogzz wrote:
Mandrake wrote:Can someone tell me exactly where it is on a 2 litre 8 valve petrol engine ?
Hello Simon,

Picture showing where the Bitron is on the petrol cars.

This Bitron fault is my little favourite.
It causes the STOP light and small light inside the temperature gauge to come on at the same time, and also causes the fans to go to the high speed, but not always coinciding with the lighting of the warning lamps.

Thanks for the info, I rushed out to my car all enthusiastic with ideas of checking out the sensor, but alas, my fuse box seems to be *completely* different to the one in your picture

There are a whole bunch of relays and gizmos but I'm no further ahead in locating it. See the following pics of my fuse box:

http://homepages.igrin.co.nz/simon/imag ... sebox1.jpg

http://homepages.igrin.co.nz/simon/imag ... sebox2.jpg

I also couldnt see any wires heading off under the headlight, although I didn't actually take out the headlight...

Regards,
Simon

Richard Gallagher · Post by **Richard Gallagher** » 28 Dec 2005, 20:02

Mandrake wrote:I also couldnt see any wires heading off under the headlight, although I didn't actually take out the headlight...

Regards,
Simon

That gives you a good idea of how inaccessable it is

IIRC the wires run across the car underneath the headlight/bumper. Even with the headlight removed only half of it is visable.

Clogzz · Post by **Clogzz** » 29 Dec 2005, 10:11

Richard Gallagher wrote:Just to confuse matters I have found the Bitron control box for the fans/aircon under the headlight on a 97 2.0 16V petrol

Lovely, and thank you for telling us about that.
I was basking in the idle comfort of thinking that there were only 2 possible locations for one single Bitron, depending on the sort of engine.
Now I can go exploring for a second Bitron, and if I find one, then try to work out what it's doing.

The Haynes book that I have, #3082 published in 1996, does quickly mention that only air conditioned cars have the Bitron, and equally quickly refers all servicing of it to the main dealer.
We know what that means: « Here mister, new Bitron, and you’re ‘done’ ».

Clogzz · Post by **Clogzz** » 29 Dec 2005, 10:29

Mandrake wrote:*completely* different

Hi Simon,

And my commiserations for that.

It looks like Richard's horror stories will prevail.

I remember a story on Planet Citroën Forum about there being a connector on the inner wing to pass the wiring to the Bitron inside the inner guard, and the connector causing intermittencies.
That forum has become a rat's nest, but if I find anything of use, I'll post it.

Regards,
Terry.