V6 Xantia Cooling Fans

Unread post by **DHallworth** » 16 Mar 2008, 18:00

Hi Guys,

My mum has a 1997 R Reg (series 1) V6 Xantia Exclusive.

Whenever she starts the car to go anywhere, or even leaves the ignition on the 2nd stage before engaging the starter motor her fans are flying at full blast.

Have had a quick search and cant find anything. The problem i had was my fans wouldn't spin at all.

It's only done 27k and it immaculate in and out so fingers crossed its nothing serious.

Thanks in advance!

David.

Unread post by **CitroJim** » 16 Mar 2008, 18:05

Hi David,

That sounds very much like a failed Bitron Sensor. I'm not sure where it is on a V6 but it'll be somewhere in the vicinity of the top hose/thermostat and it'll be a brown sensor.

Do a search on Bitron and lots of topics will come up on it. Basically, if the Bitron sensor fails open-circuit the fans default to a fail-safe full speed condition to guard against overheating.

The other possibility is bad connections on the Bitron control unit which normally lives down under the N/S headlamp and gets covered in muck and road spray.

Unread post by **xantia_v6** » 16 Mar 2008, 20:33

Do the fans still run with the A/C turned off?

The bitron sensor is on the thermostat housing, but is a bit inaccessible without removing at least the airfilter box, and probably the throttle body.

Unread post by **DHallworth** » 16 Mar 2008, 22:01

Yup, no matter if the Air Conditioning is on or off the fans are constantly on at full speed.

David.

Clogzz · Unread post by **Clogzz** » 17 Mar 2008, 14:02

By the way of air conditioning, a faulty pressure sensor switch may also cause the fans to spin flat-out as soon as the key is set to ‘ignition’.
The pressure sensor plug has 4 wires, 2 thick ones to operate the compressor, and 2 thin ones to operate the fans at high speed in case of overpressure.
Unplugging the pressure sensor should stop that.

I’ve had the high fan speed fault come and go on my Xantia, caused by a dodgy crimp connection in the socket on the inner guard near the battery:

http://www.frenchcarforum.co.uk/forum/v ... hp?t=23458

Unread post by **RichardW** » 17 Mar 2008, 14:58

Hmm, odd one this.... If the temp sensor was faulty then I would expect the fans to run all the time - regardless of the ignition status - but on the other hand I would not expect an A/C fault to influence the fans if the A/C was off - although maybe the high pressure switch is wired such that it gives full fans regardless of the A/C switch position. You may also be caught if this is a MK11 car - the A/C comes on at demist position, without any warning lights.....

Clogzz · Unread post by **Clogzz** » 18 Mar 2008, 13:44

would not expect an A/C fault to influence the fans if the A/C was off

Neither would I, but I must say that I don’t know.

Would have to do some map reading or experiments to find out.

If the temp sensor was faulty then I would expect the fans to run all the time

This one I’ve had cause to find out.
The Bitron has two supplies, one of them permanent, allowing the fans to run at the low speed on the accessory position, and also with the key out, for a maximum timed to 6 minutes, says the book.
The high speed can only operate on the ignition position, from the switched supply.

As a stopgap fiddle to prevent the high speed from operating unnecessarily until I could fiddle with it, I did this bodgie, which made it impossible for the fans to run at the high speed.
The same can be achieved more quickly by removing the high-speed wire from the 3-way connector dangling near the battery, but there’s the risk of ‘mullering’ the plug/socket.
It’s still like that now, and changing it back will get its turn some day.

Unread post by **RichardW** » 18 Mar 2008, 15:18

"The high speed can only operate on the ignition position, from the switched supply"

I know for certain that on my 97 MK1 VSX TD that wasn't true - I pulled the connector off to find out - fans roared into life. They also wouldn't stop till I switched the ignition on - was getting ready to disconnect the battery

Unread post by **RichardW** » 18 Mar 2008, 20:42

I looked in Haynes - NBG

Surprise

Might be time to fork out £3 for an hour on citroen.service and see what wiring diagrams specific to the V6 you can snaffle?

DickieG · Unread post by **DickieG** » 18 Mar 2008, 21:00

Wiring diagram for the Xantia cooling fans http://www.peugeotlogic.com/workshop/ws ... fanop1.htm

Unread post by **RichardW** » 19 Mar 2008, 07:50

Nice one Dickie. Assuming that does apply to the Xantia (probably knowing PSA!) then it's got to be a fault with the HP switch / wiring on the A/C. My reading is that the HP switch is the LH one of the two shown, and this will bring on full fans at key on if it's made. This function is independant of the Bitron (although the Bitron would receive a signal to say the HP switch is made, and presumably cut the A/C compressor). Simply unplugging the pressure switch on the A/C drier should quell the fans if this is the case.