Xantia cruise control repair

[Mandrake]

Today I thought it was about time (nearly a year and a half after buying it) to have a serious go at tackling the non-working cruise control on my S2 Xantia V6, which has never worked since I've had it...

I used Citrojim's excellent guide below:

http://www.frenchcarforum.co.uk/forum/v ... hp?t=33767" onclick="window.open(this.href);return false;

Rather than following the guide step for step I decided to do the easiest things first and work my way towards the more difficult, because I'm fundamentally a lazy person.

For me the easiest thing to do first was electrical tests from the ECU connector, but finding it proved to be the first challenge. According to Jim's guide the ECU is under the carpet under the drivers seat... not on my car it isn't !!

After considerable head scratching and going back and forth between Jim's guide and the vague location shown on the Sedre wiring diagrams I realised that it's in fact inside the centre console behind the rear electric window buttons, so is easily accessed by removing the tray behind the window buttons and the buttons themselves.

Wiring diagrams for my car, Series 2 RPO 7905 taken from Sedre:

https://dl.dropboxusercontent.com/u/782 ... nciple.pdf" onclick="window.open(this.href);return false;
https://dl.dropboxusercontent.com/u/782 ... lation.pdf" onclick="window.open(this.href);return false;
https://dl.dropboxusercontent.com/u/782 ... Wiring.pdf" onclick="window.open(this.href);return false;

I diverged somewhat from Jim's testing procedure, the first thing I tested was the power feed between pins 10 and 8 with the Cruise switch enabled - check.

Next I tested for power between pins 9 and 8, which should be present with cruise control turned on and the brake pedal NOT pressed - fail. This comes through relay 7307 and switch 2100 which is in the brake pedal. I checked on pin 1 on the brake pedal connector and had 12 volts, on pin 3 nothing with the pedal pressed or not pressed, so as suggested in Jim's guide the brake pedal contacts were faulty.

I pulled the brake pedal switch apart and cleaned the dirty contact with emery paper as recommended and the brake switch is now working properly. Reassembled and plugged back in, we now have 12 volts on pin 3 of the brake pedal switch when its NOT pressed, as it should be. One fault fixed.

I then returned to pin 9 of the ECU - still nothing. Hmm. Relay 7307's coil is powered by the same cruise switch that supplies power to pin 10 of the ECU so I know that switch is ok, I know the voltage out of the brake pedal switch is now ok, so either the relay or the wiring to it is faulty.

Now the fun begins, because I'm not actually sure where it is! Jim's guide says in S1 cars its above the right hand wheel arch liner, and S2 cars have it in the drivers foot well relay area. Mine is a S2 car, yet the diagrams from Sedre with the correct RPO number entered (linked above) clearly show relay 7307 mounted above the wheel arch liner.

Further confusion surrounds pin 6 and 7 on the ECU - according to Jim's guide the function of these two is opposite in S1 and S2 cars - in S1 pin 6 is electrovalve and pin 7 is motor, in S2 pin 6 is motor and pin 7 is electrovalve. (Trust Citroen to do something like this!)

Well in my car pin 6 is definitely the electrovalve, and pin 7 is the vacuum pump, consistent with S1 wiring despite being a S2 car, yet the wiring diagram from Sedre for the correct RPO says that mine should be wired opposite, eg in S2 fashion! So the wiring diagram definitely does not match my car, which makes me question whether it has the correct relay location or whether the diagrams have that wrong too. (Although the fact that the pinouts match S1 configuration would tend to suggest it is in fact in the S1 location, eg above the wheel arch)

It's a bit of a pain to take the wheel arch cover out and I don't have a spare relay so I decided to leave the relay investigation until tomorrow - I'll go and buy a relay and have one on hand when I take the wheel arch liner out so I'm not having to do that twice...

I then turned my attention to the pump, dump valve and diaphragm. Not having a small battery to connect to the ECU socket as Jim's guide suggests, I used power from pin 10 of the socket itself.

With pins 6, 7 and 8 bridged together (earthing the earth returns of the vacuum pump motor and its solenoid) and pins 10 and 1 bridged together via about 3 metres of cable, I was able to stand and listen under the bonnet while I connected and disconnected the power, and confirmed that the vacuum pump is working. It's kinda hard to miss really, its rather loud!!

If I put my finger on the diaphragm I could feel it pulsating but there wasn't enough vacuum to activate it. On a previous occasion I've checked all the vacuum hoses and they're all in good condition, on the right spigots, and all nice and tight, so I don't think its a vacuum leak with any of the hoses.

To check the diaphragm was ok I disconnected the hose from it, opened the throttle wide, put my finger on the hole and it holds the throttle open without any leakage, so no vacuum leaks in the diaphragm itself.

Next I checked the vacuum pump and its electrovalve separately - which is how I found pin 6 and 7 are labelled incorrectly on the diagram as pin 6 is definitely the electrovalve and 7 the motor itself. There is a distinct click from the electrovalve, so I'm assuming for now its ok. The electrovalve draws about 170mA, and the motor itself about 400mA.

Next I disconnected pins 6, 7, 8 and just supplied power from pin 10 to pin 1, which should operate the separate dump valve, as its earthed through the chassis. Nada, nothing. With my long wires I was able to lie under the corner of the car and listen while pulsing it on and off and couldn't hear a thing, so it looks like the separate dump valve is not working.

It does seem to be drawing some current though - about 30mA which isn't really enough for an electrovalve, so I'm hoping its just a corroded connection. I've previously had the connector off the valve and sprayed it with contact cleaner, but I didn't realise at the time that the earth return goes via a chassis lug somewhere, so that could be where the fault is. Either that or the dump valve is faulty.

So that's where I'm at at the moment. So far I have found three individual faults - brake pedal switch, cruise control relay and dump valve, all faulty, no wonder it wasn't working!

I think the ECU is working ok though because if I'm driving above 25mph and I try to activate it a relay in the ECU box clicks, then clicks again if I press the brake pedal or pull the cancel direction on the stalk, so at the very least its sensing speed and inputs correctly. I've also ohmed the control stalk to check the switches - at first they were very "scratchy" probably because they never get used, but after a few minutes of working the stalk in every direction the contacts now seem fairly reliable. I've run out of contact cleaner so I can't spray the switch just now.

Hopefully tomorrow I can find where this relay is and fix/replace it leaving just the dump valve, which I'm not looking forward to as access is terrible especially when you're working on the pavement!

If the relay is in the drivers foot well area I have no idea which one it might be since the wiring diagram doesn't show it as being there...there are also two empty relay sockets in the foot well area, not sure if that's normal!

[Stempy]

I had a problem with the relay on my Xant. It's a grey one I think and you can swap it with the one next to it, though at the moment I can't remember what that one does. What I did as a temporary fix was to drill a small hole in the top and squirt it full of switch cleaner which brought it back to life until I got a replacement. You can get to the pump fairly easily with the suspension on high. I did a running repair at the roadside on mine whilst on holiday when the hose split. Stick a jack under it too obviously. The electrical connector to the pump also needed cleaning at a later stage in it's life.

Very glad to hear on another thread that she's still running and been fitted with a manual box, so real hooligan tackle now;-)

[addo]

It's a violet relay near the OBD socket. I resoldered a lot of iffy looking joints on the Hella PCB.

[Stempy]

Actually, come to think of it, it might have been the brake pedal relay that I replaced, but it was in the same location down by your feet.

[Mandrake]

It's a violet relay near the OBD socket. I resoldered a lot of iffy looking joints on the Hella PCB.

Don't think its that one on my car Addo. The relay by the OBD socket is green and seems to do something else. I'll double check though. (Is there any significance to the colour of the relay or is that just Citroen being cute with all the different colours)

Is there any way tin Sedre to start with a relay and work backwards to find out what it is, or would you just have to go through all the wiring diagrams looking for one that used that relay location ? (like looking up a name from a number in a telephone book...)

It could be that my car is an early transitional Series 2 that still has a Series 1 cruise control design with the relay above the wheel, at least that's what Sedre is suggesting..

[Ben82]

Is there any way tin Sedre to start with a relay and work backwards to find out what it is, or would you just have to go through all the wiring diagrams looking for one that used that relay location ? (like looking up a name from a number in a telephone book...)

Doesn't look like it...However... if you can find the wire numbers on the wires, you can look these up in SEDRE under tools - Code Headings... which might give you some insight into what the relay is and which diagram they pertain to.

[Mandrake]

If I can find the wire numbers on the wires ? Are you 'aving a laugh Ben ?

Tiny little numbers printed near the ends of the wires going into the relay socket that I could only see if I removed the whole fuse panel ? No thanks

[Ben82]

If I can find the wire numbers on the wires ? Are you 'aving a laugh Ben ?

Tiny little numbers printed near the ends of the wires going into the relay socket that I could only see if I removed the whole fuse panel ? No thanks

I did say "if" Wasn't aware they'd be so difficult to find (Though it is Citroen, a bloody oil level plug isn't in the easiest of places )

[Mandrake]

Yes, even if I took the fuse tray out there's no guarantees the writing on the wires would be legible, from what addo has said before it often rubs off.

I think what I'll do is carry on under the assumption that the diagrams are right and that its above the wheel arch and see if I can find it there, but I'll get a new relay first so that if I'm right I can test/swap it and reassemble in one go. (seriously, who designs cars with relays above the wheel arch liner ???! )

[addo]

The wire numbers are throughout the wire's length.

The relay socket colour is supposed to infer the relay colour. You can also test continuity from the push switch to the relay socket pins. The actual vacuum pump motor is all but bulletproof.

[Mandrake]

So the colour coding of the relays doesn't imply any significance to electrical characteristics of the relay (current rating, internal diode, number of contacts etc) outside of Citroen, just a colour code to match the colour of the socket ? I ask because most replacement relays are black...

Yes I'll do some multimeter checks at the socket of that green relay by the fuses before pulling the wheel arch liner off just in case its the one, it should be easy enough to take measuremens from there to the brake pedal switch, ECU connector, and also measure the voltage from the cruise switch, so I'll know right away whether its the right one or not. Murphys law tells me that it'll be above the wheel arch liner though..

[addo]

I don't think you'll find any relays there. Are you sure your car is a S2? The wings are the same on a V6, so it could be a re-dressed S1 - does it come up as a series 2 on Service Citroën?

The sockets are a nominal colour grading so far as I can determine, the whites seem to be intermittent switching, then purple, green black in order of current capability.

[Mandrake]

I don't think you'll find any relays there. Are you sure your car is a S2? The wings are the same on a V6, so it could be a re-dressed S1 - does it come up as a series 2 on Service Citroën?

Yep, it does. Check for yourself:

VF7**************[VIN obfuscated, can be read by forum staff]
RPO 7905

Now check the Sedre wiring diagram for the cruise control for that RPO and tell me where it shows the relay...(not that there couldn't be a mistake, I've already found one mistake in the wiring diagram)

It's definitely a Series 2 - S2 headlights and bonnet, RF remote not infra-red, air bag instead of grab rail above the glovebox, Hydractive switch on the dash instead of the centre console, outside temperature by the clock instead of in the speedo, digital trip counter instead of manual, transponder key for immobiliser, "Exclusive" not "VSX" etc...

The only thing I can think of is that because its a very early S2 (first registered August 98 and built who knows when) it might be transitional and have some S1 artefacts, like the cruise control layout. I think we all tend to assume that certain things change exactly on the S1/S2 boundary, but maybe sometimes that's not the case and some things carry over for a while or change early depending on what parts stocks they have left.

Edit: according to an ORGA calculator I found, 30th June 1998 was the date of manufacture.

The sockets are a nominal colour grading so far as I can determine, the whites seem to be intermittent switching, then purple, green black in order of current capability.

Right, so Citroen has their own dinky colour coding scheme for the type and rating of relay that isn't industry standardised ? So as long as I replace it with a relay of suitable current rating, diode (if needed) and number of contacts I should be fine...

[addo]

Citroën's relay colour coding is designed to ensure an inadequate current capacity across the range of electrical loads. Many of the relays have an internal diode already. Generally I'd suggest you go over spec with a known brand of item when replacing.

[Mandrake]

Citroën's relay colour coding is designed to ensure an inadequate current capacity across the range of electrical loads.

I bet they were also rubbing their hands with glee when they came up with the idea of mounting electrical terminals and relays above the mud flap on a front wheel - what could possibly go wrong ?

Many of the relays have an internal diode already. Generally I'd suggest you go over spec with a known brand of item when replacing.

Yes, the one that needs replacing is a 4 pin type with an internal diode indicated on the diagram,so I'll need to get one with a diode. If its in the fuse tray it will need to be a fairly short one too or the flap won't close...