Simon's new Xantia V6 and Leaf blog

Tell us your ongoing tales and experiences with your French car here. Post pictures of your car here as well.

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Mandrake
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Re: Simon's new Xantia V6 blog

Post by Mandrake »

Just to make sure I don't get bored due to a lack of car repairs, my ABS decided to throw it's toys out of the pram on the way home. :twisted:

The warning light came on and stayed on permanently as soon as I turned on the key and started the engine. I was initially worried that my gentle wire brushing of dirt and rust from the sensor rings when I did the discs recently might have done some harm but then I realised that a warning light that appears and stays on before the car has even moved can only be an electrical fault.

I popped it on the Lexia when I got home to see which wheel was to blame, which then proceeded to lead me on a merry chase! :rofl2:

The recorded faults were:

"Fault: Front right wheel sensor's signal above 40 Km/hr" and "Fault: Front right wheel sensor's signal outside the tolerance".

Not exactly what I was expecting to see for an open circuit sensor... additionally when I used the parameters measurement feature to measure each road wheel speed during a test drive all wheels seemed normal...great, an intermittent fault... #-o

Even stranger, as soon as the fault re-occurred during driving the reported wheel speeds would suddenly jump to 93kph for LHF, 56kph for RHF and 50kph for both rear wheels, all whilst I was driving at a random speed around 30-40mph, and the readings would stay stationary at these figures even if I pulled over.

In fact even clearing the faults would not allow the speed measurements to start working again - the key had to be turned off and on after clearing the faults... Initially I thought it might be a snapshot of the reported wheel speeds at the instant that the ECU detected a fault, but in that case the wheel speeds pointed at the front left wheel being faulty (as the odd one out) not the front right!

Due to the uncertainty of which front wheel it might be I decided to return to the trusty old ohm meter :lol: which quickly confirmed the front right sensor (pins 1 and 6) being completely open circuit. So I guess that's what it is...

Does anyone know off hand where the connector is for the front right sensor and how difficult it is to get to so I can try some contact cleaner on it ? Failing that I guess it's a new sensor! :roll: I tried wiggling the cable between the bulkhead and the hub a couple of times and it remained open circuit (although driving the car will get it going again for a while) which makes me lean more towards corrosion in the connector than a break in the cable where it flexes.

Also any recommendations of where to get a good quality front right sensor, for a Series 1 Xantia V6 ? Are all Series 1 Xantia's the same or does the V6 have specific sensors ?

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xantia_v6
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Re: Simon's new Xantia V6 blog

Post by xantia_v6 »

It is a while since I dealt with Xantia ABS, the sensor is not V6 specific, but there are I think early and late mk1 sensors (the V6 being late).

The RH connector is relatively easy to reach, just follow the cable above the subframe.

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Re: Simon's new Xantia V6 blog

Post by RichardW »

Like to keep us on our toes, don't they?

For MK1:

96 113 241
WHEEL ABR SENSOR AV
- UNTIL RPO 06443

4545 43
- SINCE RPO 06444

MK2 is a different part number.

Here's a genuine one of the later MK1 type (which I guess yours will be): http://www.ebay.co.uk/itm/454543-ABR-WH ... SwT5tWPmrp for only about 1/3 of the RRP (£66)

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Mandrake
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Re: Simon's new Xantia V6 blog

Post by Mandrake »

Thanks Richard - that's the one, my RPO is 7515.

I decided to just go ahead and order it as chances are reasonably high that it does need replacing and I don't want to be chasing an intermittent problem with the brakes for weeks wondering whether I have really fixed it instead of just making it less intermittent...

Does the same sensor fit all wheels or just the front ?

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Re: Simon's new Xantia V6 blog

Post by RichardW »

Just the front (both sides the same), rears are different.

I had another thought - I remember Peter saying he has fixed them in the past by cutting back the cable till it's OK, then soldering in a length of new co-ax to prevent having to remove the sensor at the wheel. Getting the bolt out in one piece can be, er, trying..... :roll:

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white exec
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Re: Simon's new Xantia V6 blog

Post by white exec »

I think that a good sensor should read 1050ohm, but do check.

superloopy
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Re: Simon's new Xantia V6 blog

Post by superloopy »

Coincidence Simon ... my abs light came on this morning and stayed on too [emoji6] I know that 454543 part number off by heart and also remember i think pins 1 & 6 at the connector. Am i right? Or is that nsf. Dont bother trying to fix the cable. Its simple enough, even for me to do a front sensor. Good job it wasnt a rear. I'm hoping mines a front when i get time to check.

Sent from my LG-D855 using Tapatalk

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Mandrake
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Re: Simon's new Xantia V6 blog

Post by Mandrake »

Doing a cut and join would require careful heat-shrinking to keep water out (inside a wheel arch is a pretty hostile place!) and would significantly reduce the flexibility of the cable, so I'd be reluctant to do that. I'll just bite the bullet and replace the whole thing. [-o<

Yes pin 1 and 6 is the front right wheel, which is the one that has failed for me. The good ones all measured 1160 ohms.

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Re: Simon's new Xantia V6 blog

Post by Mandrake »

The ABS sensor arrived yesterday so next fine day that I'm off it will go in, hopefully without too much of a fight! :roll: I notice that the new sensor does not come with a mounting bolt so I hope the old one is usable and doesn't shear or round off during removal...

Before I've even had a chance to fit the ABS sensor the car decided to throw me a second curve ball - we were heading out only a mile from home queued in a traffic jam when the coolant temperature warning light and the STOP light started coming on and off intermittently. I rolled the windows down and could hear the cooling fans were running permanently on high speed even when the warning light wasn't lit. Sigh. #-o

The temperature gauge was also reading unusually low despite us being more or less stationary - it usually reads around 70 but it was not even going that high. So I turned around and crept slowly home, being reasonably sure that it was a sensor fault and not an actual overheating condition, since the gauge sensor and fan sensor are two separate sensors - genuine overheating should cause both the warning light (from the brown fan control sensor) and the gauge (from the blue sensor) to read high, but the gauge was quite a bit below 70.

I popped it straight on the Lexia when I got home and it showed the reading (from the green sensor) was normal - around 90 degrees despite the fans still going at full speed and the warning light flickering on and off. After stopping the engine I gingerly opened the filler cap to make sure the low coolant sensor wasn't triggering the warning light but the coolant level was fine. Phew! No problems with the cooling system just a dodgy output from the brown sensor, which is a common problem. [-o<

So out with the infamous air filter box to see if the brown sensor can be reached without a major strip down - which it can, just. :)

The brown sensor can be seen peeking out near the middle below the hose clamp:

Image

My intention was to give the connector contacts a good clean with LPS 1 in case they had some corrosion on it. To my surprise I discovered that this sensor isn't directly connected to the wiring loom, but rather comes via another seemingly unnecessary black connector, shown unplugged above, something I haven't seen mentioned before. So there is a short patch lead between the sensor and the main loom:

Image

The significance of this being that anyone cleaning the connector on the sensor itself who did not notice this extra connector (and I did not notice it on my previous V6 when I did the same job) would fail to clean the connector on the black plug as well - which is also a potential source of trouble. Whoops.

Anyway both connectors were duly cleaned (although they did not look that bad to me at all) and refitted. Along the way I discovered a rather nasty problem with the connector for the knock sensor when I went to refit it!

Image

The large protective moulded rubber block is completely ripped open, right down to the point where the cable inside is fully exposed. #-o Fortunately the wire's own insulation is not pierced, but the cable as a whole is not protected. It seems pretty clear that it has been damaged by the hose clamp sticking out behind it when someone has had it in and out:

Image

I don't know whether I did this on a previous occasion (I definitely didn't do it today) or whether it was already like that. I didn't have time to try to repair it today and I'm not sure of the best way to fix it - maybe a bit of oil resistant silicone in the crack ? Or maybe try to glue it back together with super glue ? I'm not sure.

I put everything back together and tested carefully - fans not coming on when they should not and no warning light. =D> I tested the fan activation temperatures by comparing with the green sensor reading given by the Lexia:

Low fan speed starts at 93 degrees and goes off at 90 degrees, high fan speed starts at 98 degrees and goes back to slow at 95 degrees, which is spot on from what I remember.

We then went back out in the car and went about our day albeit an hour late... 8-) No problems at all, and I noticed a very interesting thing. The temperature reading on the gauge, which as pointed out by xantia_v6 and others, partially measures the temperature of the water returning from the radiator, has always read quite low on this car - it never reads above 70 unless you work the car hard in which case the reading goes up to about 80 or in extreme conditions 90 tops.

After fixing the fan control signal this has changed - the temperature is now rising to an indicated 80 or maybe slightly above and is staying very steady around this point neither rising or falling much despite changing driving conditions and it is not dropping back to a reading of 70 anymore - at least not at speeds below 30mph. And remember I have not touched the blue sensor for the gauge which is on the back of the head and difficult to reach anyway.

And I'm pretty sure I know why - I believe that long before it started causing the warning light to flicker and the high fan speed to come on when it shouldn't the poor high resistance connection was also causing the low fan speed to come on too early and prevent the engine from warming up properly when the car was only being driven moderately at slower speeds.

The sensor is a PTC so higher resistance is interpreted as a higher temperature, this is why unplugging the sensor causes the fans to immediately go to full speed - open circuit is interpreted as a very high temperature. But what happens if we just add some resistance in series with the sensor ?

This will make the fan controller think the temperature is higher than it really is with the effect of causing the low fan speed, high fan speed and warning light to all come on at lower temperatures than they should, but otherwise appear to be functioning normally.

The low fan speed was quite possibly coming on before the engine was even fully warmed up when the thermostat was barely starting to open, so during slow around town driving the fan running would prevent the engine reaching operating temperature. The slow fan speed is too quiet to be heard while driving the car, even with the windows down so would go unnoticed.

Because the gauge temperature shows a blend of engine temperature and radiator return temperature, the fan running when it shouldn't would cause an unusually large drop in the return temperature indicated on the dashboard gauge that wasn't necessarily reflected by the Lexia reading. Now that this is not happening the engine is able to reach proper operating temperature on the return side as indicated by the gauge as well.

The funny thing is only a couple of weeks ago I checked for a stuck open thermostat by holding the top radiator hose from a cold start to see if it stayed cold and then went suddenly hot after about 10 minutes as it should - and it did, showing that there is no leakage through a slightly stuck open cold thermostat. I did this because it seemed like it was taking far to long to reach full indicated temperature with slow driving. Now I know why! :)

So in summary:

1) Even if it has not yet got bad enough to make the warning light flash or the fans to obviously go on high when they shouldn't, if there is resistance from a bad connection it will lower the threshold temperatures for the fan speeds enough to prevent the engine from warming up properly under light loads - check and clean the connectors anyway, especially if your temperature gauge reads unusually low!

2) The terminals didn't look bad to me at all - if anything there was maybe a very fine white powder appearance to them, but nothing that I would say was obvious corrosion. And yet cleaning them solved the problem, so there was definitely a bad connection there. Use a good electrical contact cleaner.

3) Don't forget to do the joiner connector as well as the one on the sensor!

4) You can check normal operation by comparing fan speed activation temperatures with the coolant temperature reading of the Lexia. On mine after repair slow started at 93 and fast started at 98. In the other direction it went from fast to slow at 95 and stopped at 90. If yours come on at a significantly lower temperature there is probably an issue with the brown sensor or its connections!

Hope this is useful to others, especially if your V6 seems to take too long to warm up...

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DHallworth
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Re: Simon's new Xantia V6 blog

Post by DHallworth »

That brown sensor on the Activa needs replacing, I've got a brand new genuine sensor to go on it (they're NFP now but I sourced mine from a dealer in Northern Ireland who had one on the shelf) but it looks to be a pig of a job to swap it!

David.

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Re: Simon's new Xantia V6 blog

Post by Mandrake »

Hi David,

What symptoms are you seeing that make you think the brown sensor needs replacing ? Have you also had the fans coming on too early ?

I know you were having problems with the gauge reading unusually low but the gauge runs off the blue sensor on the rear.

I'm not sure how you would get at the brown one to replace it without removing the upper air intake manifold, or at least removing the butterfly assembly. If you could remove it with a socket drive it would be fairly easy but it requires a spanner at the base of the sensor and I don't think there's any room to swing a spanner without a reasonable amount of disassembly around it. :(

If you are seeing a similar problem to me (warning light and/or engine running unusually cold) it might be worth trying to clean both the connectors before going as far as replacing the sensor, as I think it would require a coolant drain down as well as some disassembly.

Try plugging the Lexia in and noting at what temperature the fans turn on to slow and then fast - if it's close to the values I reported its probably not faulty!

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Re: Simon's new Xantia V6 blog

Post by xantia_v6 »

I have (on 2 occasions) changed the brown sensor with only the air filter box removed. I used a deep socket with a short extension. Releasing the clip on the connector with a screwdriver was the tricky part.

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Re: Simon's new Xantia V6 blog

Post by Mandrake »

So I tried to fit the ABS sensor today and predictably ran into trouble. :roll:

First let me say whoever designed the location of the ABS sensor connector on the V6 Xantia didn't seem to consider the possibility that it might need to be unplugged during the service life of the car... :rofl2: I'm sure it's a bit easier on some other models of Xantia where there is more room, but on the V6 it is tightly wedged in between the suspension chassis, engine mount, drive shaft, exhaust pipe and exhaust heat shield, which surround it on all sides...

I have fairly skinny hands but I really struggled to even reach it at all, not to mention trying to press the wire clip down and pul the plug off (which can move less than an inch before it fouls on something else) and then try to get the plug to release from the retaining clip on the chassis...got there in the end though.

I was extra careful about not rounding the hex off the bolt, using plenty of penetrating spray, wire brushing the nut, working the nut gently in both directions etc, only to have the bolt shear instead. #-o :evil:

Image

So, what next ? It's a 6mm bolt and I've drilled a 3mm hole through the middle of it hoping that what's left would fall out but no dice. Is the only solution to buy a tap with the right thread and tap out what's left of the bolt ? :?

Mumble mumble...

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Re: Simon's new Xantia V6 blog

Post by RichardW »

Bugger, said Dougal.... pretty normal I think though. You might get it out with an easy-out, but you definitely don't want to snap one of those off in there - so probably best just to drill it out to the right dia and re-tap it. The bolt is still available from Cit for yours - alternatively you could just fit a normal bolt - and if there is enough room at the back it might be possiible just to drill it oversieze and fit a bolt with a nut on the back - which is what I did on the 307 when I broke one when I was changing the wheel bearing - although it was rather easier with the hub on the bench!!

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Re: Simon's new Xantia V6 blog

Post by NewcastleFalcon »

Mandrake wrote: So, what next ? It's a 6mm bolt and I've drilled a 3mm hole through the middle of it hoping that what's left would fall out but no dice. Is the only solution to buy a tap with the right thread and tap out what's left of the bolt ? :?

Mumble mumble...
You could always try this if you are good at welding, or know somone who can do it for you...looks very straightforward "on the bench". I got my rear caliper bolts removed with a similar technique, but away from an electricity supply my "welder" had to use Oxy Acetylene which reduced some of the nuts to liquid before we got it right :)



Regards Neil