French electrickery

[Derekofpriory]

Our Xants been having a rest for a few weeks, we have the use of our youngest sons 57 plate Octavia deisel whilst he and his wife are in Kenya for a six month tour with the army. Hard seats and firm suspension isn't comfy like the Xant
Anyhow, to business, Shirley decided to take the Xant to tesco for a trip out. when she got back she was a very cold unhappy bunny no heater fan at all.
Basic checks, a, was fan switched on? yes.
b,Pull all fuses one at a time, no blown fuses, sod it no easy fix!
c, Right lets put some music on while I think about finding my way to the blower, ignition on enter code and as the radio started so did the blower motor had a quick look at the BoL but I'm not good at following wiring diagrams, my eyes don't do straight lines very well, they much prefer curves!
Not really looking for answers just muddying the waters for those who say there's a logical explanation of everything,-provided you exclude french wiring!!

[VertVega]

This sounds somehow very familiar. I recall reading several topics on this and the reason of this problem was
told to be the ignition barrel. It prevents the heater blower to turn on and also no power to the rear heated glass.
I didn't have this problem (touch wood ) but I guess it can happen also in MK2 versions.

I didn't read more carefully but I saw some instructions separating the power supply to the blower and using
some relay/fuse combination. In a pic. location shown was below the steering column.

[citroenxm]

As its a S2, it has the "Relay" mod as standard, my guess is with the car standing the relay failed to evergise when it was first used...

Then switching the key again got it going.. so a few flicks of the key has got it going again..

Paul

[C.J.]

Our Xants been having a rest for a few weeks, we have the use of our youngest sons 57 plate Octavia deisel whilst he and his wife are in Kenya for a six month tour with the army. Hard seats and firm suspension isn't comfy like the Xant

Skodas? I know, and still do after 4 years of ownership.
Cracking cars, but granted, not as comfy as a Xantia....nothing is.

Sorry, bit off topic but couldn't resist.

[Derekofpriory]

I'm not sure if I may ask another question, but someone will tell me if I shouldn't have.Vehicle is Xantia 2.0 Hdi 90 V plate 99.
The engine does not overheat even towing our caravan, but we have had a temperature stop flash for at least the last three years, previous to that it was intermittent, the temp. gauge hasn't worked for donkeys years. Now that the xant is a spare car I can work on it without time pressure to get all the electickery niggles sorted. When the fault was intermittent it could be triggered by setting the heater vent to demist, count to seven and the stop would flash, move the slider to centre count to ten and it stopped flashing. Turning aircon on had the same effect. Most of the time the nearside fan was running on high speed the offside one didn't run at all. I got another from a local scrappie, fitted it and reassembled most of front.
When I started the engine both fans went to high speed and stayed there, when I stopped the engine both fans dropped to slow and were still running 3 Mins after removing the key! Disconnecting the battery allowed the relays to drop out and the fans stopped.
For the fans to stay on low speed with Ignition off would indicate an alternative power supply for the control unit to enable it to short pin 1 to earth. A short to earth on the wire between relay terminal and the control unit would mean that the fans would restart when the battery was reconnected.
As to why the fans run at high speed, the controller must believe the engine is overheating, i.e low resistance across the temperature sensor except that a year or so ago the engine management light came on, and a quick trip to our local fuel injection specialists revealed that most of the problems were unimportant. All faults were cleared and one stayed, the ecu believed engine temp was -50 degrees! this made me think the temp sensor or its wiring was open circuit, this would explain the lack of movement of the temp gauge.
Confused doesn't begin to explain it.
It will get another dose of looking at next Wednesday afternoon if the weather is reasonable, I anyone could suggest a few tests to make I would be very pleased, I have multi-meters and lots of electrical bits around and am a fairly competent rough engineer. I am toying with the idea of a lexia but haven't learnt enough about the limitations and strengths of them yet.

Cheers Derek

[citroenxm]

Thats the useual thing that is being discussed on a Xsara thread...

Its useually the control relays that sit between the cooling fans!!

One leg on one of the 3 relays will be burnt or something..

Here


Unless Ive missed a point and you have already been here..

Paul

[Clogzz]

Since both fans can spin at both speeds, and also when the engine is cold, we have a temperature sensing fault.
The HDI has a single ‘does-it-all’ blue temperature sensor, and it’s either faulty or has an intermittent connector or wiring.
Not sure about the blue sensor, but the finding with PTC sensors is usually 1900 Ohms when cold and 3500 Ohms when hot.

The fans must go to low speed when the aircon is on, and sliding to windscreen demist also turns on the aircon.
The fans can spin for about six minutes at low speed after turning the engine off, even with the key out.
That’s controlled by a part of the ECU that has a permanent supply.

[Derekofpriory]

Thanks Clogzz,
It has to be a temp. sensing fault as you say, and I prefer to blame the wiring rather than the sensor itself, the car is ex Lex Leasing and according to the service printout had been fitted with 3 temp sensors by different main dealers before we got it at 3years and 2 months old.
Main problem now is finding circuit diagrams for the all singing and dancing multi purpose blue temp sensor, all diagrams I have found on here are for the multi sender setups, and the BoL only shows sensors with2 terminals, so if anyone can give us a hint where the 2 light green and single yellow wires send or receive electrickery from it will make my endeavours later this week more effective. I assume I have a Bitron and will try to get there first to check continuity and corrosion, next stop will be the ecu cable end, and then if really have to, get to the inst. cluster wiring to see if I can trace back the Coolant temp gauge wiring.

[Clogzz]

Hi Derek,

Three sensors over the first three years obviously means factory fault.
I suspect a crimping fault at the ‘other end’ of the sensor.
The HDI and all the single-blue-sensor cars don’t have Bitrons.
They’re controlled directly by the ECU and the intermittency is likely to be at that end of the sensor wires because we should expect the sensor changers to have stretched the wires at the sensor end to find the break.

I had a three-sensor petrol Xantia with and intermittent crimp in the connector passing the sensor wires through the inner wing behind the battery.
My multimeter said 1.2 Ohms with joined probes, and one sensor wire measured 3.7 ?.
I soldered a thin wire around the break and it’s been good since.

Our chief Jim has an impressive collection of maps, but I can't find them on his site yet.

Enjoy a good fiddle.

[Derekofpriory]

Thanks Clogzz, Luckily there was enough brightness and warmth to make our allotment a nicer place to be this afternoon rather than under the bonnet . So I haven't started looking for a non-existent bitron, one less thing to go wrong . If the cables go through the inner wing behind the battery, does anyone have any idea what route they may take to get to the ECU. And just to ask a bonus question where might I find a pin-out diagram for the ECU, to enable a test feed to the temp gauge, and to trace back to the temp. sensor. I am sorry if I am taking up too much time but I really would like this sorted.

Cheers everyone, Derek.

[Clogzz]

Hi Derek,

My story of sensor wires passing through the inner wing is for my Mk I petrol with the Bitron in the fuse box.
The loom to the right of the battery tray passes through the inner wing.
I’ve never had the chance to properly explore the engine room of an HDI, so don’t know which way the sensor wires go, and hope that those in the know aren’t far behind.
Hope you can spend another nice afternoon in your allotment.

[Derekofpriory]

Hi all,
Got to the blue sender, couldn't find anything totally amiss, three wires are connected - two green and one yellow-, I am guessing that two wires are connected to a thermistor and one to a switch to earth one of each go to the ECU (the thermistor wires?) and are showing less than 0.5 Ohms end to end. The remaining green wire (switched?) heads towards the nearside inner wing connector, wire shows low resistance sender to connector. Next job is to get the wheel off and inner wing out and trace that one, but, if both connections to the ECU are OK. and the ECU controls the fans why are they still acting up? Thinking in print now, slower but clearer than thinking out loud if there was a wiring problem between ECU and fan relays could that do it? and what does the third wire do anyway and where is it heading. Wire number I think is 401. I don't think Old Speckled Hen will help my brain work better but I might as well try a couple tonight anyway

[Clogzz]

Hi Derek,

The thermistor is inside the blue sensor, that’s how it senses.
The wire going to the inner wing may operate the high speed.
The high speed only needs one wire to switch from low to high speed.
On the Mk I, the fan control wires were dangling in front of the battery.
We would need to find the map to go further.

[Derekofpriory]

Thanks Clogzz, Rereading my last post I could have expressed myself a lot more clearly, thoughts of a couple of Hens addled the brain cell .
I realise the thermistor is in the sensor and its resistance appears between two terminals of the ECU via one green and one yellow wire, these both are in good condition. The remaining wire from the sensor must be switched to earth to change the fans to high speed connection and since the wire is not heading to the ECU how does the control signals get to the relays?

Cheers all,
Derek.

[Clogzz]

Hi Derek,

Switching to earth is used to go to high speed.
Same for the low speed but the earthing there is coming from the ECU.
The top right relay as seen from the front has a permanent supply and is energised by the ECU earthing the low end for low speed.
For high speed all three relays are energised and the remaining wire from the sensor is going to the relays through the inner wing connector.
There are maps of the Mk I fan control in this topic:

http://www.frenchcarforum.co.uk/forum/v ... hp?t=31403

The HDI fans are the same except for that there’s no Bitron, so no help with the blue sensor wires.