Xantia ventialion system blows cold with aircon on or off.

Gordon W · Post by **Gordon W** » 10 Aug 2006, 23:42

It's a 1997 R reg 2.1TD VSX, and I've just had the aircon recharged, and the cabin sensor cleaned without solving the problem, but costing me about £180 in toto for 2 visits to the garage which claims to be a Citroen specialist.

The problem is that with the temp slider set at the recommended 22 degC and the aircon either on or off, the ventilation system only passes cold air. This is at ambient, or maybe a bit cooler without the aircon working, and flippin' cold with the aircon working.

Only when you advance the temp control slider to over the 26 degC setting does the air begin to warm up, and with the slider fully to the right, hot air eventually arrives. Outside air temp is around 20 degC

Clearly the cabin temp control isn't working, though the aircon will produce freezing cold air.

A related problem is that with the blower on auto, it used to eventually slow right down when the cabin temp had stabilized .... it just keeps right on blowing strongly now, though as it's blowing freezing air I turn the blower off before I freeze too; so it doesn't get a chance to stabilize.

The garage comment ref the work carried out on the cabin sensor is as follows:

"Checked heating parameters, found cabin sensor was reading a constant 25 degrees no matter where the slide control was set.
"Stripped out sensor and found that the impellor was jammed, cleaned out and tested, refitted and checked system
"Sensor now reads within 1 degree of slide control setting"

I'd be very grateful if anyone could give me a steer on how to fix the system myself, seeing as the mechanic had never heard of the Bitron sensor 'till I aired my knowledge of it gleaned via its brief mention in the Haynes manual.

Best regards and thanks in advance

Gordon
Devon, England

AndersDK · Post by **AndersDK** » 11 Aug 2006, 00:29

Gordon -

I've moved "you" to the aircon forum.
Browse this forum - and you may hit your luck.

Post by **RichardW** » 11 Aug 2006, 09:08

I's still reckon the internal temp sensor is up the swanny. Once the fan stops going round there's little you can do about it, except replace. If you shine a torch down the grille around the alarm LED and switch the ignition on and off you should see the fan start and stop. You may find it appears to run OK when cold, but if you check it after a half hour drive it will have stopped. The heat from the stalled motor and radio causes the sensor to mis read. A new one from Citroen is about £85, so mine's been hanging out of the dash for about 6 months, strapped onto the side of the heater controls, where it seems to work fine 8)

alan s · Post by **alan s** » 11 Aug 2006, 10:42

Just a thought, but if the fan that circulates the air over the sensors is caput, wouldn't that kinda stuff everything be it hot or cold and may explain this situation?
(Quite prepared to accept arguments to the contrary.)

Alan S

Gordon W · Post by **Gordon W** » 11 Aug 2006, 12:20

@ Anders: Many thanks for the re-direction and I've had a good read 8)

@ Richard and Alan: Thanks for your help. I just had a 15-minute session in the driveway with the engine running at tickover. I looked into the grille with a torch but couldn't see an awful lot, though my aged eyesight is not what it was even with specs on.

Initially the cold air problem was there, so I bashed the grille thingy and everything started to work: both the aircon and non-aircon air temps faithfully followed the slider.

I would like to remove the grille thingy to have a better look inside. What's the thread-to-the-needle explanation of how to extract the grille? The garage mechanic told me that I should be able to flip it out without having to remove the radio etc as described in the Haynes manual, but that hasn't worked. Can I lever the thing out with a screwdriver without breaking anything, and if so where do I insert the lever?

best regards

Gordon

Post by **RichardW** » 11 Aug 2006, 12:46

I couldn't get mine out without removing the radio and the clock. Assuming it's a MK 1 - Open and remove the ashtray (if you've not done this before it's a bit odd - press the tab down, but then lift UP the tray!). Undo the two screws you can now just about see in the top of the tray. Prise off the radio / heater control surround. Undo the two screws and pull the radio out, then disconnect the wiring plugs - press the lever in and wiggle the plugs out. Remove the Radio surround (4 screws now revealed). Reach through the hole and push the clock out and remove it. You should now be able to wiggle the sensor out - it might be a tight fit though and need pushing up at the back while you help the front out with a screw driver. You probably need to pull the plug off the side of the radio aperature in order to be able to disconnect it. You can separate the two halves of the sensor carefully - the back half has the fan and the temp sensor sticks forward towards the grille. Try routing it out past the radio, and seeing if that fixes the temp control.

If it's a MK11 things are a bit more difficult I think.

Gordon W · Post by **Gordon W** » 11 Aug 2006, 14:52

Oh dear. That sounds like another upside-down session inside the car! The last time was when I cut off the air-bag plugs under the front seats and soldered the wires together to cure their intermittent connection which kept causing the airbag lamp to blink.

My Xantia (which I do like a LOT for its comfort and towing ability) is the Mk1 - it has the black plastic trim and bumpers. I bought it 3 months old pre-registered in 1997 and it's only done about 73000 miles so far. It's in very good condition and I hope to keep it at least another 8 to 10 years.

I've done most of the normal servicing (oil & filters) on it myself, but had the cambelt and hydraulic oil changed by the garage at 60k due to its low miles-per-year. Now I've found this forum I think that I'll be doing those next two changes myself, but thankfully they're some time off!

Gordon

Gordon W · Post by **Gordon W** » 14 Aug 2006, 17:15

Before dismantling the facia to get at the sensor and its fan, I thought that I'd try a little experiment first

I velcro'd a small computer fan to the facia in front of the grille, and powered it from the cigar lighter.

A pic showing the arrangement is here: http://www.putfile.com/pic.php?img=3201293

Believe it or not, it got the aircon working properly

So now I need to decide when to do the job properly.

Thanks for your help guys!

Gordon

Post by **RichardW** » 15 Aug 2006, 12:55

Nice 8)

Not sure if it's better or worse than my solution!

It might take an hour to get the sensor out the first time, but you can mostly do it sitting in the driver's seat so it's not too bad. The £85 for the new sensor is though

Clogzz · Post by **Clogzz** » 15 Aug 2006, 15:16

It’s been years since I fiddled with that, but I think to remember that the sensor will come out when prising it out along its right side edge with a flat-bladed ¼ inch screwdriver.
The sensor and motor will then dangle out from a long enough piece of loom.
The motor will benefit from a very good squirt, because it’s in the habit of stopping and restarting all by its little self.
Sealing the metal joints of the motor housing with silicone will keep it quiet.
A strong blow into the sensor grill will clear it of accumulated dust.
It’s a good sign that I don’t remember well, because it was a long time ago, and haven’t been there since, an indication that the fiddle has paid off.