Xantia Aircon Compressor Operation

Post your Cit/Peu/Ren air conditioning queries or advice.

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dch-control
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Xantia Aircon Compressor Operation

Post by dch-control » 02 May 2007, 21:42

Hello,

I have a 1998 Xantia Desire Estate, 1.9TD and the aircon compressor does not kick in. Both radiator fans operate at low speed whenever I switch on the aircon on the dash, and the internal blower is spinning OK. If I remove the Bitron sensor plug both radiator fans run at high speed and the Bitron sensor itself has a resistance of about 1800 ohms, so that all seems OK.

On this car the Bitron relay is in a lovely clean plastic enclosure at the front off-side of the engine bay. This enclosure also contains a Bosch electronic control module (which I presume is the climate control computer?) and a normal relay. This relay is energised and I have taken it out and checked it for correct operation.

If I pull the connector off the compressor there is no voltage on the incoming wires. If I apply 12 volts to the compressor terminals it engages and starts to spin. With the connector back on I have tried by-passing the pressure switch contacts on the bottle with the sight glass but I just can't get the compressor to cut in.

Do you think this is likely to be a problem within the climate control unit or is there something else in the external wiring that I could check? I've pulled the multi-way connector off the control unit and checked that all the contacts are clean and all the wires are correctly terminated inside the connector.

Any helpful comments would be appreciated.

Thanks,
David.
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Post by CitroJim » 02 May 2007, 21:56

Hi David,

A very warm welcome to the forum :)

You've done all the basic checks so now it is time to go deeper.

Have a browse through the Aircon section of this forum. It is a goldmine of information.

Alans and Cloggz from Down Under are our resident aircon specialists and no doubt, once they wake up, they'll tell you all you need to know.

There are circuit diagrams of the Aircon wiring and ECU connections in the aircon area of the forum and these should help enormously.
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Thanks

Post by dch-control » 02 May 2007, 22:31

Thanks for your welcome.

I have worked my way through the air-con forum as well as this one and found some useful stuff. As a matter of fact I did have a problem with the cooling fans and found a circuit diagram that helped me get them sorted. (It turned out to be a corroded plug contact but armed with the diagram I could see how they were meant to work).

I'm a bit stumped with the compressor problem though so I'll go to bed hoping that someone on the other side of the world is sorting it all out for me!

David.
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Post by Mandrake » 03 May 2007, 03:43

Hi David

When you checked shorting the contacts on the dryer bottle pressure switch, did you do it for long enough ? Later Xantia's (about 1995 on I think) have a 3-4 second delay in the compressor activation.

There are four contacts, the pair on one side (thick wires from memory) activate the compressor clutch when shorted, the other pair should immediately put the fans into high speed if shorted.

If you measure the contacts on the pressure switch are the two going to the thick wires shorted ?

Also, when you manually powered the compressor clutch was the air conditioning otherwise functioning ? (EG producing decently cold air)

I agree with Citrojim - there are a LOT of air-con threads on here with good info if you're able to find them with the search function.

Regards,
Simon
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Post by Clogzz » 03 May 2007, 17:34

This map shows most of what there is to the air conditioning controller:

Image

All the maps and pictures that I have are in this bucket:

http://s132.photobucket.com/albums/q23/Clogzz/
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Disaster...

Post by dch-control » 03 May 2007, 17:36

Hello,

Thanks for your reply. I'm sure I wasn't shorting out the pressure switch circuits for long enough before - I didn't realise there was a delay. I repeated the check today and if I short the thin pair of wires the radiator fans do indeed go to high speed. If I short the thick wires, however, the compressor does not run even if I wait 15 seconds or more. The pressure switch contacts that go to the thick wires are shorted.

To answer your question about whether it cools properly when the compressor is made to run I decided to put power directly on to the compressor again. Unfortunately, when I did so the other day I didn't pay attention to polarity of the power supply and I didn't remember which way it was connected. I guess I must have connected it the opposite way today because I seem to have blown something up. I fried the temporary connecting wires and the compressor now reads a dead short, whereas the other day I'm sure I measured it at about 6 ohms

I suspect there is perhaps a suppressor diode across the clutch windings and I have now destroyed it. This is going from bad to disastrous! I've left the wiring loom disconnected from the compressor while I decide what to do next. I guess the compressor will have to come off to have a look at the clutch. Of course, this is just a diversion - I'm still no nearer to solving the original problem.

Further encouragement urgently required.

David.
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Bad timing!

Post by dch-control » 03 May 2007, 17:41

Ah Clogzz,

Thanks so much for your reply. If only I had waited another few minutes before trying things I would have seen your post and observed the diode shown clearly on your diagram.

Ho hum...

David.
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Post by alan s » 03 May 2007, 21:06

Whoops, sorry to be a bit long winded getting back, but I've had a couple of dramas including getting a new innards in the computer which resulted in loss of a few things including log in info etc, so I managed to lock myself off the forum :oops: (fortunately we have checks and balances to get around that) and have spent most of the week installing and commissioning solar heating panels to my existing hot water tank....(don't ask) :roll: :evil:

Back to this air/con problem. I would have gone as you have by firstly testing the HP/LP control on the receiver dryer and as you suggest, a direct feed would be next option.
If there's still no joy once you get back to this, check the lead where it attaches to the compressor for internal breaks and then next cab off the rank is the actual solenoid to the clutch itself.
Depending on the brand of compressor, removing the clutch can range from difficult to almost impossible, but as far as I know, all can be removed. I recently was at a guys place who had ripped one out in a matter of minutes.

Always check the "exciter" fan which sits behind that postage stamp sized grille just above and to the left of the radio. If that little fan isn't going, the rest of the system can throw some weird symptoms from all accounts.


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Post by Kowalski » 04 May 2007, 10:03

alan s wrote:Depending on the brand of compressor, removing the clutch can range from difficult to almost impossible, but as far as I know, all can be removed. I recently was at a guys place who had ripped one out in a matter of minutes.


The clutches are easy to remove from all of them, just so long as you have the right tool. The right tool is a suitable puller, I had to make one to get the clutch off a Harrison one, kits are available to buy in the US to take apart the whole compressors, but I couldn't find one in the UK.
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Post by fastandfurryous » 04 May 2007, 10:35

The first question to ask, which hasn't been asked yet: Is there enough refridgerant in the A/C circuit to actually allow the compressor to run. If the LP switch on the drier bottle is open, then the compressor clutch will never engage, as the system thinks there's insufficient refridgerant.

Of course, by forcing the clutch to engage with a direct feed, you can find out if the clutch works or not, but if you do this, and engage the compressor with little/no refridgerant in the system,(and the engine running of course) you may damage it.
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Post by Mandrake » 04 May 2007, 10:59

fastandfurryous wrote:The first question to ask, which hasn't been asked yet: Is there enough refridgerant in the A/C circuit to actually allow the compressor to run. If the LP switch on the drier bottle is open, then the compressor clutch will never engage, as the system thinks there's insufficient refridgerant.

Check David's responses again - that question has indeed been answered - the contacts on the switch that operate the compressor measure shorted (as they should) therefore there is enough gas in the system for it to activate, were it not for the fault condition. (Which must be somewhere in the climate control system, if the pressure switch and the clutch solenoid are both ok)

Commiserations on getting the polarity to the clutch wrong David - mistakes happen sometimes thats life....not sure what to suggest to repair that - if you can get at the diode it could be replaced, but at the very least you're going to be looking at a regas of the system afterwards with no certainty that it is going to work or that the original problem can be easily found..... :?

Regards,
Simon
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Post by dch-control » 04 May 2007, 11:25

Just a quick reply to answer the points that have been raised.

I'm confident there is plenty of gas in the system: (a) the pressure switch seems to indicate so, and (b) the system was re-gassed less than a year ago.

At that time, the garage that re-gassed it observed that the compressor didn't seem to be running as often as it should (although it did run). I suspect this was the first sign of a fault that has changed from intermittent to permanent.

As regards the little exciter fan, how do I check this please?

Thanks,
David.
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Post by Mandrake » 04 May 2007, 11:31

Shine a torch into the little grilled hole next to the clock - and you should see some tiny fan blades, if they're not turning, its seized/faulty. Mine turns but sometimes buzzes noisily.

One possible fault is the icing sensor on the evaporator - if the evaporator temperature drops too close to freezing it will switch off the compressor clutch to prevent the evaporator from freezing up - and if that temperature sensor is faulty it could prevent the clutch from activating at all.

No idea exactly how you get to that sensor on the Xantia though or what it looks like - it might be a dashboard out job to find it - and a fault in the climate control unit could give the same symptoms. :?

Does anyone have any experience with this sensor ?

Regards,
Simon
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Post by AndersDK » 04 May 2007, 11:40

The dash sensor is located just next to the little fan.
Its been discussed before. Use the forum searh feature and I'm sure details will show up.
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Post by fastandfurryous » 04 May 2007, 15:51

Mandrake wrote:the contacts on the switch that operate the compressor measure shorted (as they should)

Ah... I see. I misread that as "they have been shorted out" rather than "they measure closed circuit"

plus if it's been recently regassed.....
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