Aircon problems: External temperature sensor on 52-reg

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My Name: Mattius

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Hi,

I've recently got my hands on a 52 registration SX C3 (1.4 petrol) which is beginning to turn into a bit of a money hole. My latest problem with it is with the external temperature sensor.

To cut a long story short, the aircon on the car was working during the test drive but not when I picked it up, so I thought it probably needed re-gassing. I called out Aircon Direct (https://www.ac4cars.co.uk/) who told me that the nearside (passenger side) mirror was missing the temp sensor. He called Citroen & ordered a replacement but the header plug on the replacement sensor doesn't fit (the sensor's header is a 2 wire job with 2 holes, the door trim's header has 4 wires going in to a 4-wire header but only 2 pins in that header). Additionally he's tried a few other things but the car doesn't seem to recognise that there is anything there.

Apparently he's able to get -1, +17 and +38 (deg C) from the ECU but none of these are correct. I'm also unable to get anything from the center display, the "tick box" button does nothing even with the car started.

Any ideas?
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My Name: C3CAR

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Model: C3 2002-2005, Original shape model
Year: 2002 (02)
Engine Size: 1.4 (16v)
Fuel Type: Diesel
Mileage: 140000
Trim Level: Exclusive
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Hi Mattius, Welcome to the C3 forum!

On my 52 plate diesel C3 the outside air temperature sensor is in the OS (Drivers side) on a right hand drive car.

Here is a picture of the exposed Exterior C3 Temperature Sensor:

Image

I have not had a look inside either side, so I can't say what the connections look like, but I am surprised citroen supplied the wrong part if they know the registration or vin number. Right part, wrong location?

The temperature sensor in the Right hand door mirror (UK drivers door) is a two wire unit that runs to the BSI (a Green and a Violet wire) according to the wiring diagram.

The C3 is well known for having problems with the BSI - Body Control Unit - Its an onboard computer, and the fusebox in the glovebox:

Citroen C3 fusebox in the glovebox 2002 - 2009
Citroen C3 fusebox in the glovebox 2002 - 2009


from the fuse box locations post:
Citroen C3 2002 to 2009 Engine Bay Fuse Box Locations

Odd readings, things not working for no apparent reason, strange electrical problems are often tracked down to a faulty BSI. The Citroen C3 BSI is hard coded to the car ECU (and then to the other computers in the car) , you can't just put any old BSI in and expect it to work.

"Additionally he's tried a few other things but the car doesn't seem to recognise that there is anything there" - seems like classic BSI problems as settings are stored in the BSI and most of the control comes via the BSI.

Both the Air-Con and Onboard display units look like they are connected to the BSI.


Its worth doing the obvious, like checking all the fuses are OK, both fuse boxes!
Citroen C3 Fuse Box Locations

Oh, and there is a procedure that resets the BSI computer, which may clear some soft faults:
Citroen C3: How to reset the BSI

Good Luck!
My Name: Mattius

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C3CAR wrote:Hi Mattius, Welcome to the C3 forum!

On my 52 plate diesel C3 the outside air temperature sensor is in the OS (Drivers side) on a right hand drive car.


Hi and thanks for the quick reply! Also I'm sorry about not replying sooner, it's just that it's been a bit too windy around here lately for me to remove the panels.

Anyway, I've had a look at both wing mirror housings and on the left (nearside) I've got one small hole. On the right (offside) I've got the same small hole plus a bigger one, just like in your picture. I've also removed the trim from both sides, the offside looks like:
C3 off side door panel
C3 off side door panel
With a close up of the connectors looking like:
C3 offside door panel connections close up view
C3 offside door panel connections close up view
So far so good, both green and purple wires there but...
C3 near side door panel connections to mirror
C3 near side door panel connections to mirror
Closeup:
C3 near side door panel connections for mirror close up view
C3 near side door panel connections for mirror close up view
Same colour wires on nearside as well, so I can see why both Citroen & the aircon guy were confused. I would of also tried the sensor in the offside panel today but as you can see from the close up, the aircon guy appears to have taken the plug off. :o So I'm going to have to tin the ends and make up a new plug first. :x

Oh well for what it's worth here's what the external temp sensor looks like:
C3 external temperature sensor for mirror
C3 external temperature sensor for mirror
Closeup:
Citroen C3 external temperature sensor close up
Citroen C3 external temperature sensor close up
And if anyone else has to do this, you'll need to buy some of these:
Citroen C3 door panel trim clips that break off
Citroen C3 door panel trim clips that break off
Trim clips. You get 7 per panel and even though I used a trim removal tool some still broke off. Little Barst... :x
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My Name: C3CAR

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Model: C3 2002-2005, Original shape model
Year: 2002 (02)
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Fuel Type: Diesel
Mileage: 140000
Trim Level: Exclusive
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: DV4 16-valve diesel (90 PS)
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Hi Mattius,

Thanks for the pictures!

With a little help I can say (with a high degree of probability) that:

On the Brown plugs, the White and Yellow/Green wires are connections for the heated mirrors (powered by the rear window heater circuit) and the Violet and Green pair run the motors to retract and extend the mirror units (e.g to protect the mirrors when parked)
These could well be an option, as you car has nothing connected to the brown plugs. I am guessing that you can't retract the mirrors from within the car or that they are heated.

The Near Side black plug has 3 wires entering the plug and 3 wires exiting toward the mirror (Red, Brown, White) for mirror adjustment.

The OS Black plug looks promising, as from your pictures you can see the Off Side door has 5 wires entering the plug, but only 3 exiting towards the mirror (Red, Brown, White) for mirror adjustment.

My suggestion would be that the Off Side Black plug, when opened has two spaces spare for the temperature sensor wires (probably pin 4 and pin 5) (pin 2 is not used) and the picture currently shows the temperature sensor on the wrong side of the car. Probably the Green and Grey wires in your photo of the black plug (if they are in positions pin 4 and pin 5 then its definite)

The wires on pin 4 and pin 5 of the black plug go directly to the BSI (fuse box/computer in the glove box).

This would explain, where is the missing plug for the temprature sensor is, as it has bare ends - the answer is that the plug is in the black socket and currently has Red, Brown, White wires populated. The sensor is probably supplied with bare ends to allow fitment to the existing plug and the plug didn't get cut off.

You can get C3 Door Panel Clips from here and here, from amazon
My Name: Mattius

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Hi C3Car.

C3CAR wrote:I can say (with a high degree of probability) that:

On the Brown plugs, the White and Yellow/Green wires are connections for the heated mirrors (powered by the rear window heater circuit) and the Violet and Green pair run the motors to retract and extend the mirror units

I thought this as well. IIRC only the Exclusive trim as folding heated mirrors and mine's an SX so that makes sense.

C3CAR wrote:The Near Side black plug has 3 wires entering the plug and 3 wires exiting toward the mirror (Red, Brown, White) for mirror adjustment.

Again makes sense. X & Y axis with a common neutral.

C3CAR wrote:My suggestion would be that the Off Side Black plug, when opened has two spaces spare for the temperature sensor wires (probably pin 4 and pin 5) (pin 2 is not used)

From what I remember, both black and brown plugs had 2 pins missing in the center (on both sides of the car):
C3 Offside Brown Plug Close Up with Annotations
C3 Offside Brown Plug Close Up with Annotations
But the plug which was attached to the sensor (I saw it, the aircon guy showed it to me as he wasn't sure how it was supposed to fit into any of the headers) was flat, much like the space marked above in blue. When I get the plugs soldered on I'll give all the possibilities a try. Do I need to reset the BSI after every attempt or can I just plug away and test?
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My Name: C3CAR

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Engine Size: 1.4 (16v)
Fuel Type: Diesel
Mileage: 140000
Trim Level: Exclusive
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: DV4 16-valve diesel (90 PS)
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You shouldn't have to reset the BSI at all. It seems as if the BSI is trying to do its best without the sensor connected and is not showing signs of being locked up or corrupt.
My Name: Mattius

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I've been a bit busy recently but here's a quick update:

Sensor's leads now have sockets attached & I've tried all combinations of all pins in both offside headers. I didn't get anything from the center console but then I assume that you need to have the car started to see anything? A quick test with the multimeter shows 0.01v across some pins, which goes higher (0.02v) with the ignition started.

Also I was slightly wrong about the black header, it's difficult to see but there are 5 pins in there.

And I'm now convinced that the aircon guy has managed to get a piece of trim clip stuck in the inter-panel door cavity - the nearside window won't go fully down and it looks like it's hitting/jamming on something. Grrrrrrrr.... :x
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My Name: C3CAR

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Posts: 2708
Joined: Wed May 04, 2011 10:01 am
Model: C3 2002-2005, Original shape model
Year: 2002 (02)
Engine Size: 1.4 (16v)
Fuel Type: Diesel
Mileage: 140000
Trim Level: Exclusive
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: DV4 16-valve diesel (90 PS)
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A 2002 C3 (Exclusive) with outside air temperature sensor. The plug with the 2 black wires will be the sensor and is located behind the passenger door card as seen in the pictures above.
Outside air temperature wiring connector
Outside air temperature wiring connector
The plug has been disassembled slightly to get a better view
My Name: samstagmoonyham

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Model: C3 2002-2005, Original shape model
Year: 2003 (53)
Engine Size: 1.4 (8v)
Fuel Type: Diesel
Mileage: 100000
Trim Level: Desire
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: DV4 16-valve diesel (90 PS)

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C3CAR wrote:A 2002 C3 (Exclusive) with outside air temperature sensor. The plug with the 2 black wires will be the sensor and is located behind the passenger door card as seen in the pictures above.

Image

The plug has been disassembled slightly to get a better view
are the yellow and green wires for power and earth? and where do they go exactly?
thanks
Edit: i may have figured it out, Are they for heated door mirrors?
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