Xantia 1.9TD Series 2 - Air-con odd problem FIXED

JamesQB · Post by **JamesQB** » 15 Jun 2009, 23:18

Hi,

Done a search for this, found circuit diagrams of system and printed them, but can't fathom what's going wrong. Here's the situation: The air-con doesn't work when you start car and put it on. The revs are always 1000 with air-con off, and stay at 1000 when button is pushed on. No cold air comes through. However, when you are driving along, it works normally (albeit not as cold as it should be - needs topping up).

When it was taken to be regassed, the chap said he couldn't do it as the compressor wasn't running. This would be true, as when idling the air-con doesn't work. I don't understand why the revs don't raise when the air-con switch is put on, like the old '95 1.8i used to, and why the air-con only works when driving and not at idle. I am thinking along the lines of the revs being too low at idle for it to activate, but high enough when driving. And I'd assume this is normal insofar as the revs should rise when air-con activated and the ECU won't allow the compressor to be engaged until that condition is met.

I checked the triple-pressure switch with engine off and found pins 1+2 short, which I believe means there is enough gas pressure and so the compressor clutch will be engaged. 3+4 were open, which I also assume is normal, from the schematic, and that they close if there's a problem and cause the fans to spin at the highest speed.

Any idea if idle without air-con should be 1000rpm, and why they aren't rising when the air-con button is pressed? If it helps at all, the engine is hardish to start warm or cold (usually second crank gets it), with engine seeming to dip before catching properly and revs stabilising at 900. Once the throttle has been touched, revs go to 1000 and that remains the idle speed throughout. This may be a separate issue completely - the hard starting. Incidentally, earlier today I found, by chance, a cable not connected to the injection pump. It should have gone to a small lobe which had about 3mm of movement only. The other end of the cable went to a vacuum-operated device which presumably pulls the cable when vacuum present. A solenoid from a group of two seems responsible for supplying vacuum to this device. No idea what it does but reconnected it. No noticeable difference to anything.

Also, car kicks out cloud of smoke when you accelerate a bit sharpish. In need of a can of treatment, or is this something to do with what I've read as 'pump timing'? Car is very clattery, like metal against metal, when idling, becoming much quieter as you rev.

Sorry for long post!
James

dieseldoggy · Post by **dieseldoggy** » 16 Jun 2009, 02:13

thats the cold enrichment device.gives you fast idle. one end has that cable which go's lever you found behind pump and other has a vac pipe which goes to valve (2 on bar next to LHM tank)other does EGR valve.fast idles set about 1000 then when warm the electro valve opens the vacuum pulls that cable in which then slows idle down 850ish.it's all linked with ecu/solenoid/throttle positsion sensor thats the thing with 3wires on top of throttle arm. if its noit connected properly ie not getting vac you will be on fast idle whole time and advanced fueling.which gives you that problem. how long you had car? as some people play with those bits when they fail.the esv fail but normally meant to be better than earlier ones.ones blue&others green. air.con should still work at normal idle.and has you said the clutch closes the idle will go upto meet load.as it loads up compressor but not over 1000rpm.

Sl4yer · Post by **Sl4yer** » 16 Jun 2009, 06:33

Hi James.

It might be worth having a read of THIS thread, particularly the post on the third page, if you haven't already.

James

Post by **Peter.N.** » 16 Jun 2009, 09:37

Could be a problem with your alternator, check that you have 14 volts across the battery with the engine ticking over.

dieseldoggy · Post by **dieseldoggy** » 16 Jun 2009, 11:07

Paxman Power wrote:1996 Xantia 1.9TD Hatch XUD with Bosch pump.

My solution to this problem was based on the fact that there is only one electrical thing directly connected to the throttle - the potentiometer on top of the pump.

I fiddled with this many years ago when trying to get the tickover speed down from permanent fast idle. Had no effect until I understood the purpose of the electrovalves and vacuum system which actually controlled the idle speed. It was only by accident that I discovered that by rotating the potentiomener that the electrovalve activated and the idle speed dropped to normal.

Since that time various vacuum hoses have died and the car runs at fast idle all the time. Will need to sort it some day!

At MOT time last month the car failed on excess emissions. The tester advised running the tank low and putting in a dose of injector cleaner. As the tank was almost full I decided that in order to give it a fighting chance I'd also put injector cleaner directly into the fuel filter. At the same time I also adjusted the potentiometer position. Don't know if this helped, but it went from a figure of 3.02 (Fail) to 0.79 (and a "Fast Pass" at that!).

So when this week I was trying to work out why my aircon wasn't cold I discovered, like you, that the compressor clutch wasn't kicking in at idle and only working when the revs were increased. When it was revved the clutch kicked in and the compressor ran, but only until the revs dropped again and the clutch dropped out. A slow anti-clockwise adjustment of the potentiometer with the engine running and the aircon turned on and all of a sudden the compressor kicked in.

Might be worth looking at it - especially if you have a fast idle issue as well.

They are all connected together.as i said before or should i say inter linked! bit like domino line thing? that bit on pump needs to be set with computer/reader thing. as that does idle.return gas/egr.cold running ie enrichment/fast idle/pump timing.it tells ecu speed of engine so ecu setts/reads everything else.quite often its the electro valve fails then cold starting/fast idles stays on which then up emissions.they can be changed to late ones ie HDi ones don't fit on bar but just zip tie it on. check you have or where vacuum disapears ie pump/pipes/esv? once thats working and the throttle position senser is sett correct you could find that air con will work correctly.plus emissions will be right down.the other one do's egr valve if that don't work it will run like a dog as taking gasses back into engine all the time.you can put injecter cleaner into fuel filter housing(Forte which is good) best time is when hot then take for fast run.
When had sim prob with mine.guy i use has the bosch unit which dealers use the amount of info it gives you is great and you dont realise how much each thing effects each other as you sett it up and read info coming back!. I'd get that sorted out first so engines running correctly then your playing fields abit more level?

JamesQB · Post by **JamesQB** » 16 Jun 2009, 13:01

Only had car a few months. I've looked at the recommended thread and see it's exactly what this car is suffering from. Before I start moving the throttle pot around, it'd be handy to know its function? Is it the sole means by which the car knows the pedal is being pressed and so the ECU then instructs the pump to inject more fuel? What changes when it's moved as far as the car's ECU is concerned (I know resistance across pot changes of course)?

From that thread, would I be right in understanding that the chap had no issue with the solenoid or vacuum pipes - they were okay - it was just the pot being wrongly positioned that was causing the fast idle to always be on?

Out of interest, is it purely the ECU that governs the revs increasing when air-con is turned on? If so, why doesn't it detect the revs are high because of the cold enrichment being on and allow the air-con on?

Thanks for all replies, hopefully will get this sorted, it's 36 degrees here!

MikeT · Post by **MikeT** » 16 Jun 2009, 18:29

Hi James, I've just speed-read this thread so forgive me if I'm off the mark or it's already been mentioned but...
... I read a warning (think it was the BoL) that states the Throttle Position Sensor (TPS) can only be set using some special bit of electronics kit so I'm not sure on the wisdom of your randomly moving it. I marked mine when I removed it for a clean - perhaps you could re-align it if there are any marks to go by?

If your pump is semi-electronic, it has a default fast idle setting. In other words, unless something pulls the rear control back (as should the cold-start solenoid via the vacuum) the engine will always idle high. This is independant of the cold-advance system which will most likely still be in good working order.

MikeT · Post by **MikeT** » 16 Jun 2009, 18:50

Right, I think I've got the jist of what you're asking. Allow me to explain what I know.

The two solenoids (or electrovalves) are for the fast idle and EGR. For whatever reason (I suspect heat) they tend to fail prematurely. Great news for the EGR but it means the idle will never fall back to "normal" revs as fast-idle is actually set on a spindle at the rear of pump and requires a mechanical device to pull it back off fast idle. You can test this by using a screwdriver (or whatever works) to force this spindle back - you will hear the revs drop but more importantly the noise output almost halves!

As a comparison so you're not overly worried about how noisy your engine is, this is what mine sounds like - it's on permanent fast-idle at about 1050rpm.

As a workaround, following a tip from another forum member, you can fit the vacuum pipe direct from the vacuum pump to the flying saucer which brings the idle down to about 900rpm AT ALL TIMES.

Unfortunately, I'm not informed about how the A/C works and the relation of the revs except that a worn compressor will give the symptoms of the A/C working well (very cold air) at speed but declining when idling or driving at low revs.

JamesQB · Post by **JamesQB** » 17 Jun 2009, 13:07

Hi Mike, I carefully marked the throttle pot before moving it so I can put it back in exactly the right position. Out of interest, is it easy to take off for a clean, as I wouldn't mind doing that while I'm here in Spain and have the bonnet up.

Moving it made no difference to the fast idle, so my next step is to remove and test the solenoid.

Regarding the A/C, one can actually hear the compressor clutch click in when the revs are raised, and click out when the revs return to 1000rpm. This seems an identical situation to the one from another poster who corrected it by moving the throttle pot slightly. I haven't yet tried moving the pot with the A/C on to see if it causes the compressor to click in at idle revs - every time I get ready to look at the car, someone needs to go out in it!

Thanks, James

p.s. my dad has worried, since buying the car a few months ago, about the noise it makes despite my assertions that it's normal for a TD. Your video sounded identical to this car and he is now happy that nothing is wrong (other than fast idle always on). Thanks!

MikeT · Post by **MikeT** » 17 Jun 2009, 16:31

I wouldn't bother removing the TPS, (the best I could do was to soak it in contact cleaner in the vain hope it would seep into the plastic casing and wash out any crud). But it's your choice of course, it didn't seem to hurt my car. But I do think you're barking up the wrong tree messing with the TPS setting. Unfortunately I don't have any alternative suggestions I'm afraid.

Except, I suspect the compressor (or the A/C complete) needs an overhaul. It might just need a vacuum and recharge of course.

I'm glad my video has allayed your father's fears. The digicam video is poor but the sound recording is quite sensitive. As I say, you'll be astounded at the difference in noise when vacuum is applied to the cold-start device on a warm engine.

JamesQB · Post by **JamesQB** » 17 Jun 2009, 19:40

Well, turns out the cold-start solenoid was open-circuit, whilst the EGR one was okay. So, I've re-routed the vacuum pipes to give permanent vacuum to the flying saucer. Revs are now around 850-900, depending how the car feels.

Still haven't sussed the air-con problem. Only thing I know for sure is the ECU isn't energising the pump clutch relay until revs increase beyond idle.

Seems quieter if still bit noisy and very clattery with the vacuum now applied to the flying saucer. Would like to get this air-con problem sorted as it gets very warm in that car in this weather when you stop and car is at idle for a short while. Not only that, want to get it regassed which can't do unless someone sits in car revving it high the whole time it's done. After that, it's back to fixing the door locking mechanism and changing the accumulator sphere...

JamesQB · Post by **JamesQB** » 18 Jun 2009, 15:03

Latest update: The violet relay in the engine compartment fusebox is kept energised when air-con is switched off, thereby not allowing the relay contacts 3 and 4 to close and deliver current to the compressor clutch. When air-con is switched on and everything is ok, the relay's coil feed should lose its return path via the ECU and power should flow to the compressor clutch. However, at idle this isn't happening. When the car is driving along however, the relay clearly de-energises as the air gets cold quickly.

To imitate this, I revved up while checking the voltage on the compressor clutch relay coil points in the socket (relay removed) and found the voltage didn't disappear even with me revving it and holding revs high 10 seconds. So, does it take longer before it'll de-energise the coil and bring the compressor in, or is something else happening when the car is actually being driven that causes the ECU to stop power to the relay?

The only thing that is certain is that (going by the schematic I got from this forum) the ECU isn't allowing the compressor clutch to engage by holding power to the clutch relay's coil winding. 12V is permanently going to pin 1 of the relay coil, while pin 2 is either held above ground potential, or grounded, by the ECU. In this case it's grounded, keeping the relay energised and thus not supplying power through to the clutch.

I think maybe the only solution is to get the car to a Citroen dealer and hooked up to a Lexia to see what may be causing the ECU to prevent the compressor clutch engaging.

I don't suppose anyone has the 1.9TD and knows if the revs increase when the air-con is turned on, and if that is achieved by movement of the fast-idle lobe via the flying saucer vacuum attachment? If so, the fast-idle solenoid is open-circuit in this car, only reading through a series resistor built into the body of the solenoid which is 300 Ohms. I presume this allows the ECU to determine that the solenoid is present but the coil is open-circuit. If the solenoid is used to cause slight advance of the fast-idle when air-con is on, perhaps this might be why the ECU is preventing the clutch engaging until the revs are higher like when driving along?

MikeT · Post by **MikeT** » 18 Jun 2009, 18:02

What compoments, sensors and actuators make up the circuits in the diagram you have?

JamesQB · Post by **JamesQB** » 25 Jun 2009, 12:57

Hi Mike, sorry for not getting back sooner. Left the air-con prob for a while and fixed door lock, changed accumulator sphere, bought new solenoid for fast-idle and changed that, and tried to get some sun-bathing in too! Sadly holiday comes to an end tonight, so must leave parents and Spain once again.

The diagram I'm going by is one from Cloggz's photobucket collection that I found during a forum search. It's marked as coming from Autodata and says it's for 1.9TD amongst others, up until 97 (although this car is 98 ).

It seems from the diagram that as well as other relays having a say depending on their function (triple-function pressure switch, etc) in whether the compressor clutch will come on, the ECU has the controlling say via a relay whose coil it controls. While air-con is off, the relay's coil is energised thus preventing current from feeding the clutch. Once the relay is de-energised, the contacts close and form a direct circuit to the clutch. When idling, this relay is being kept energised and so the clutch has no 12V feed to it. Revving it and holding it there a few seconds on the drive didn't cause the relay to de-energise, but when driving along with revs around 2000 or more, the clutch is clearly being given power and the air-con starts working.

I changed the fast-idle solenoid after reading that it's used to increase the revs when the air-con is on. My thinking was that the ECU could tell the solenoid was knackered and so maybe that was the reason it wasn't allowing the clutch to engage at idle. However, it's made no difference and when I started car on the drive, despite the high temperatures here, the fast idle was on. It only went off when I revved it, returning on again as soon as revs dropped back. I didn't allow the car to get upto normal operating temperature though - assumed fast-idle would only come on when air temp was low...

So, more confused than before, and now out of time. Incidentally, it's XUD9TE engine with Bosch pump, the type that has throttle pot on it.

MikeT · Post by **MikeT** » 25 Jun 2009, 14:23

Well done for finding the schematics and working out the logic control but I don't understand why the A/C would be programmed to not work at idle and don't recall my previous MK1 doing that - perhaps others can confirm this is intentional or a fault? (Meanwhile, I'll try and locate the diagram myself and get better aquainted with the circuits.)

As for the fast idle being permanently on when warm, this again doesn't sound right to me (unless it is indeed due to the A/C) though I know it should go off when revved beyond a certain point.