Xantia cruise control repair

[CitroJim]

As far as I recall it's toward the rear of the wing and high-up by the A Pillar. Not so far away from where the main loom turns right on it's journey to the big bulkhead connectors.

As soon as you have the mudshield out you’ll see the box..

There'll be loads of room in there for whatever relay you have...

[Mandrake]

Thanks Jim

One other question I have relates to the adjustment of the threaded plastic piece on the end of the bellows where it attaches to the throttle butterfly - how does one know how far to screw it on ?

On mine it was nearly unscrewed right off so at some point in the past when I had the manifold off I screwed it most of the way on, I realise that this adjustment sets the maximum throttle opening that the bellows is able to apply when fully contracted, but the question is where should it be set ?

Sometimes I can't help fiddling...

[CitroJim]

Good point Simon...

I always just guess it and set it so it has a bit of play in it...

Never seen any official set-up procedure for it...

[Stempy]

I always set mine for max acceleration

[Mandrake]

I always set mine for max acceleration

Sounds good to me.

[Mandrake]

Well, a few hours spent out in the sun tracing this problem today, the relay turned out to be a wild goose chase! On the up side I've now positively identified the real fault.

As expected the relay turned out to be in the plastic case above the right front wheel arch - its actually above and behind the indicator repeater at the rear of the wheel arch. When I opened the water proof sealed box I was confronted with the sight of three spotlessly clean relays, and my thoughts of oxidation of the contacts faded away:



The relay in question is the pink one on the right. Yes its on a lean because one of the terminals was a little bit damaged and was not locking into place in the socket, I've repaired that, but it wasn't the fault.

A couple of minutes of voltage checks on the relay revealed the problem - although it was getting +12 volts on pin 1 when the cruise control switch was on, pin 2 was not being earthed and also measured +12 volts. Pin 2 is not earthed directly, but goes via the normally closed contact of the starter inhibit relay (1005) to ground through the starter solenoid coil.

It didn't take me long to realise that with the key turned on the starter inhibit relay was permanently energised, not just in the starter position of the key. This had me puzzled for a while as I couldn't see how this could possibly work... I double checked the wiring diagram for the ignition switch and confirmed that the positive side of the starter inhibit relay (1005) is indeed supplied in both the ignition on and starter positions.

I then realised that the ground side of relay 1005's coil also is not directly earthed but goes to the gear shift switch. Bingo! The starter inhibit relay is energised only when the gear lever is in Park or Neutral, which enables the starter but DISABLES the cruise control!

As soon as I moved the gear lever to Drive relay 1005 turned off, and relay 7307 (cruise relay) started working as expected - energised with the key on and cruise button selected.

Additionally +12 volts is now available at pin 9 of the cruise control ECU when the cruise button is on but the brake pedal is not depressed. So there was never anything wrong with the relay, it just has to be tested in Drive not Park or Neutral.

This is such a big gotcha that I really need to post an addendum in Jim's cruise control repair thread as it is not mentioned there, and it takes patient tracing of three different sets of wiring diagrams (cruise control, starter and gearbox) to figure this out.

I could have saved myself a couple of hours of pulling the mud flap off and tracing and testing the wiring if I'd studied the wiring diagrams a bit more thoroughly beforehand, but not to worry. At least I repaired that slightly loose terminal and confirmed everything looks good in the relay box. I didn't even replace the relay as the originals are just like new so I saw no point.

So as far as I know that's all of the inputs to the ECU tested and working correctly, so I turned my attention back to the vacuum pump and dump valves.

I bridged pins 6, 7, 8 and pins 1 and 10 again as before, the latter with a long pair of wires so I could activate the pump from under the car. As before the pump and the electrovalve in the pump work ok but the separate dump valve won't click. I put my fingers over the dump spigots on the dump valve to block it off and energised the vacuum pump and its electrovalve - presto, the diaphragm opened the throttle wide up. It did take about 3 seconds to fully open the throttle, I don't know if that is a bit slow or normal, but it certainly did the job and rules out everything on the vacuum side besides the dump valve.

I took the connector off the dump valve and checked for corrosion - none that I could see and I have sprayed the connector before. I did continuity checks from the connector back to chassis earth and pin 1 on the ECU connector - both are well under half an ohm so are fine.

I've removed the dump valve completely and tested it directly on 12 volts - no click and it won't switch over. It measures about 325 ohms. So apparently I have a faulty dump valve:



Whether it should be lower resistance than that, or whether its just mechanically stuck I don't know, but it definitely doesn't work!

So now I need to get my hands on a replacement. I'll put a wanted note up in the for sale section a bit later, hopefully someone has one to spare.

[RichardW]

Surprisingly reasonable new

Part Number Description Quantity Price excl. VAT Price incl. VAT Total incl. VAT Selection
00001628L9 ELECTRO VALVE 16.41 GBP 19.69 GBP 19.69 GBP

[Hell Razor5543]

Once you get it going, watch out for Sandra Bullock and Willem Dafoe!

[Mandrake]

I never even thought to check Citroen's price Richard, I guess that's not too bad for brand new. It'll have to wait for next month though, I'm still yet to pay for the coil pack and fuel pump from KP's breaker and I'm not allowed to spend any more money on the car this month once those a paid for!

[CitroJim]

Excellent Simon..

Sorry, never occurred to me to say the relay is only energised in D... Thus it's lethal to bypass or otherwise defeat the starter inhibit relay as imagine what would happen to the poor engine if you accidentally knocked the gear selector into N when on cruise at 80!

Great that the dump valves is so cheap..

Removing the mudshield should have been a golden opportunity to get lots of rust inhibitor going aground there..

[Mandrake]

Indeed it makes sense that it would be disabled when not in gear, but the way it's spread across three different diagrams makes it non obvious how its done...

I don't suppose you have a spare valve you could measure the coil resistance of Jim ?

I'm thinking that maybe 325 ohms is plausible and that the pintle could be stuck in its seat through corrosion.

If the coil measures ok I'm thinking why not try to free it up, a squirt of penetrating lubricant down the ports, and some gentle taps on the housing with a hammer while its energised might do the trick and I have nothing to lose.

[addo]

I get 28.1Ω on my spare EV. It's made by Eaton, allegedly in Monaco!

[Mandrake]

28.1 ohms ? I guess the coil on mine is faulty then, so no point spraying it. Odd that it would be that low though, as the electrovalve built into the vacuum pump is around 150 ohms and works ok...

[addo]

I'll check another one.

[Mandrake]

I have in my possession a brand new electrovalve for the cruise control, so we should have a resolution to this thread quite soon. (unlike my other massive thread! )

I get 28.1Ω on my spare EV. It's made by Eaton, allegedly in Monaco!

Well called addo. My new electrovalve measures 28 ohms, the faulty one measures 325 ohms. Clearly an electrical fault with the coil.

What's interesting is that the bag that it came in says "Electrovalve EGR", so it would appear the same electrovalve is used in some EGR systems. That explains why its still available and not hideously expensive - if it was only used in obsolete 15+ year old vacuum cruise control systems it either wouldn't be available any more or would be ridiculously expensive!

I'm intrigued to see how well it works, I've never driven a car with working cruise control before.