Simon's new Xantia V6 and Leaf blog

[white exec]

Hi Simon,

The level sensor is either a float switch, which will be two-wire - or a conductivity sensor, which will be three-wire (like XM). The three-wire jobbie contains electronics, as indicated (but not internally detailed) on the XM circuit diagram.

You should be able to check whether it's a conductivity checker: these have two simple prongs dipping into the water. Unplugging should bring the warning light on.

Connection to the three-wire type is:
- Gnd
- +12v from IGN sw
- signal back to warning lamp, and possibly to Inj ECU as well (limp mode & reduce fuelling for the diesels).

Puzzled by the two wires, like you.
Conductivity is not enough to illuminate a tungsten dash warning light.
If two-wire, there must be some intervening electronics to operate bits upstream.
Correct circuit diagram will surely tell.

Lost my clip too on the brown plug. Plug can be held firmly in place with a piece of thin wire around the clip groove.

[Mandrake]

Hi Simon,

The level sensor is either a float switch, which will be two-wire - or a conductivity sensor, which will be three-wire (like XM). The three-wire jobbie contains electronics, as indicated (but not internally detailed) on the XM circuit diagram.

You should be able to check whether it's a conductivity checker: these have two simple prongs dipping into the water. Unplugging should bring the warning light on.

It's definitely a conductivity sensor with the two probes - same as my S2 V6 had in it. And yet the cable is only a two wire cable.

Unplugging it does not bring on the warning light, in fact it was already unplugged thanks to the missing wire clip.

Connection to the three-wire type is:
- Gnd
- +12v from IGN sw
- signal back to warning lamp, and possibly to Inj ECU as well (limp mode & reduce fuelling for the diesels).

So says the S2 wiring diagram, but my S1 only has two wires, so I don't understand it.

Puzzled by the two wires, like you.
Conductivity is not enough to illuminate a tungsten dash warning light.
If two-wire, there must be some intervening electronics to operate bits upstream.
Correct circuit diagram will surely tell.

Yes I need a circuit. I wonder if the S1 models used a float sensor and someone has fitted a S2 conductivity sensor ? Who knows.

[white exec]

Bit unlikely that Citroen went from conductivity probes in the 90s (for XM) to float switch for S1 Xan and then back to conductivity again for S2. Sounds like some bodgery.

[superloopy]

I'd be starting from the dash end and swap in a known 'good' bulb ... ok to say that it HAS worked in the past but who's to say that it's working now, you could be of on a wild goose chase for no reason ... it's just the way my brain works

[Mandrake]

Coolant warning bulb is fine - see my previous replies.

I have an idea for a test - I'm going to unplug the coolant temp sensor for the fan controller, this will bring the fans onto high speed and light the same warning light.

I'm also going to measure the voltage on the plug to the level sensor while I'm doing this - the two signals are wired in parallel to the same bulb - if the 12v drops to near zero at the level sensor plug when the warning light comes on from the over temp condition on the fan speed sensor then it probably means it is indeed supposed to be a simple float switch!

Re bodges - remember xantia_v6 has already reported a few posts ago that his S1 Xantia V6 has a two wire cable and his XM has a three wire cable, so this is consistent with someone fitting the wrong type of sensor to mine!

As the coolant expansion bottle has been replaced twice before my ownership this is certainly a possibility IF there are two different types of sensors for different age Xantia's.

I'm going to check service citroen to see if this is the case. I'm now strongly leaning towards someone having fitted a conductivity sensor to a car requiring a float level switch and not confirming whether it did in fact work.

[xantia_v6]

The switch fitted to my XM has a different part number to the one in your photo. Your photo also indicates a date code consistent with your switch being original.

[Mandrake]

Just checked on service citroen and looked up both my old S2 and my new S1 by VIN number and they both show the same sensor part that Richard originally posted - 1306 C0.

So the sensor is the correct type, but how can it work with only 2 wires, and why would the S2 wiring diagram clearly show three wires with pins 1 and 3 being power and ground with pin 2 going to the warning lamp when pin 2 is the one missing on this car ? How could the same sensor work in both situations ? It makes no sense at all.

Turning into a right old murder mystery this is.

[white exec]

Simon,
If only two wire, what happens if you connect them together (via a 12v 5W lamp for safety)? Does dash warning lamp light up?
For two wire, there are only two possible states, open circuit or closed, after all.
Any joy getting sight of a 1997 S1 circuit diagram?
Interesting that you talk about coolant tank changes; quite possible the sensor you have was imported with one of these. Sensor date is confusing, though. Was that (replacement) tank ever fitted to anything else apart from Xantia, I wonder?
C.

[DHallworth]

Glad to hear the main swapping of the radiator went without a hitch, Simon. Hopefully you'll have the confusion with the level sensor sorted before long too.

David.

[Stickyfinger]

Sorry Simon, I have been swamped with work today, I have only just finished at 12:20 pm !

[Mandrake]

The switch fitted to my XM has a different part number to the one in your photo. Your photo also indicates a date code consistent with your switch being original.

Which number is the date code, is it the 21/97 ?

Is the part number only the first line - PSA 9622507780, or does the second line 73506902 also have to match ?

The reason I ask is because the Citroen part number as found in service citroen does not turn up any real matches on Google, however PSA 9622507780 finds quite a lot of matches on places like Ebay, however the number on the second line doesn't match on the ones I have seen on Ebay. If that is only a batch code or something that doesn't matter that's fine. Do you know ?

[CitroJim]

Simon, I'll have the circuit with you soon...

[CitroJim]

Here you go Simon...

Level Circuit

Level Harnesses

Level Locations

You will see the signal from the probe is processed by the Bitron fan/AC control ECU...

It does not go directly to the instrument binnacle warning light...

[xantia_v6]

You will see the signal from the probe is processed by the Bitron fan/AC control ECU...

It does not go directly to the instrument binnacle warning light...

Actually, it doesn't... It goes directlyt to F2

So I think it is fair to say that someone made a mistake and forgot to connect the sensor to the warning light.

Is this diagram applicable to all Mk1 Xantias, or just the V6?

[CitroJim]

S1 V6 only Mike...