C5 2.2 HDi fuel filler cap sensor replacement

Post by **tmead** » 07 Jul 2010, 17:54

Has anyone changed this ? I've got an antipollution fault message, and reading codes on lexia indicates that the sensor has failed. I've takena a look at it with a meter, and on one of the connectors by the low pressure pump I see a change from open circuit to a couple of hundred ohms when the filler cap is near. I think it is a reed switch, so should drop to zero when actuated ?

The wire runs down by the filler pipe and then up over the top of the tank. The gap between the tank and body doesn't seem large enough to thread either the sensor or connector through, so I'm not sure how to change it.

I've visited Citroen parts counter today, and they have a picture of the general area with a 'harness' that looks like it takes this route, but splits to feed two connectors on top of the tank somewhere. It's around 50 quid and marked non-returnable, so I have to be sure of getting the right part !

All info gratefully received, as I'm about to chop the reed switch off the end and replace it with a cheap one from maplin spliced to the wires and sealed with adhesive lined heatshrink. Nothing to lose at the moment - it's not working right now, so can't get worse !

Tim

Post by **myglaren** » 07 Jul 2010, 19:05

This has come up previously and although I believe it is unconfirmed there was a suggestion that it was an Hall-effect sensor, not a reed switch.

Post by **tmead** » 08 Jul 2010, 09:53

All info gratefully received, as I have searched in the forum and can't find anything - must be trying the wrong terms !

Tim

alderman · Post by **alderman** » 08 Jul 2010, 09:59

Hi Tim

If you lift your rear seat up and remove the large rubber grommet in the floor, you will see the electrical terminals for the lead to the filler cap. If you disconnect these and put a multi-meter across them, the resistance should read 15 ohm with the filler cap removed and 150,000 ohms with it fitted. (At least for a Mk 1 model.)
These can go open circuit or combine somehow to about 400 ohm.

The cable cost me £32 to replace the two years ago. A bit of a fiddle to replace, but you do not have to drop your fuel tank as some threads have suggested.

I found it easier to start the cable run from the front, secured at the connector above the fuel tank and then pull the cable across the top of the tank to shorten the run. I then used a ‘fish’ wire to the pull the sensor up the wheel arch to the filler cap position. The hardest part I found was to finally re-assemble the moulding around the filler cap and also secure the cap locking relay mechanism to the moulding.

Regards
Allan

tmead wrote:Has anyone changed this ? I've got an antipollution fault message, and reading codes on lexia indicates that the sensor has failed. I've takena a look at it with a meter, and on one of the connectors by the low pressure pump I see a change from open circuit to a couple of hundred ohms when the filler cap is near. I think it is a reed switch, so should drop to zero when actuated ?

The wire runs down by the filler pipe and then up over the top of the tank. The gap between the tank and body doesn't seem large enough to thread either the sensor or connector through, so I'm not sure how to change it.

I've visited Citroen parts counter today, and they have a picture of the general area with a 'harness' that looks like it takes this route, but splits to feed two connectors on top of the tank somewhere. It's around 50 quid and marked non-returnable, so I have to be sure of getting the right part !

All info gratefully received, as I'm about to chop the reed switch off the end and replace it with a cheap one from maplin spliced to the wires and sealed with adhesive lined heatshrink. Nothing to lose at the moment - it's not working right now, so can't get worse !

Tim

Post by **tmead** » 08 Jul 2010, 10:36

Thanks Alderman,

Were there two connectors above the fuel pump ? The picture from Citroen parts indicates the sensor wire has two seperate connectors. There are several in the space above the fuel pump - lots more than on my pug 306 hdi that's for sure ! i disconnected one of them that is definitely connected to the sensor and tested it with a meter, the resistance didn;t ever drop to 15 ohms that's for sure. I wasn't expecting to find a second, so did not even try to trace out for another once I'd found one !

Trouble is Citroen want 50 quid for the part and are claiming it is non refundable once ordered. I need to be sure I'm getting the right part for that !

I'll scan the picture they let me have in a while and post it here.

Tim

cachaciero · Post by **cachaciero** » 08 Jul 2010, 11:47

You need to be careful when checking these things, this may not be a switch in the accepted sense. One of the wires supplys 5 Volts to the sensor the other is described as "signal". However another reference calls it a contact and quotes a resistance of 15 ohms no magnet and 150,000 magnet but it is not clear if this is checked with the item connected using a "breakout" or if checked O/C. One thing is clear it is more than just a reed switch, I would expect a reed switch to have a "made" resistance in the region of milli ohms and open mega ohms.

cachaciero

Edit
Might be worth checking the resistance with a stronger magnet if it's a hall effect device it will be sensative ti field strength, might be a weak magnet in the cap.

alderman · Post by **alderman** » 08 Jul 2010, 17:04

Tim

On mine there were two blue twin connectors and a separate black twin connector actually attached to the large round plastic cover. The wire number ID's on the white incomers are 738 & 733.

I've dug up my old Cit invoice and the part number is 6534HY described as a 'Loom' and cost me £27.59 + vat in Jan'09.

The circuitry is simply a 15ohm and a 150k in series with a N/C reed contact across the 150k resistor. When the cap magnet comes into influence, it causes the contact to 'open', thus presenting the ECU with a 150k + 15ohm passage, or when cap removed just 15ohm.

Regards
Allan

tmead wrote:Thanks Alderman,

Were there two connectors above the fuel pump ? The picture from Citroen parts indicates the sensor wire has two seperate connectors. There are several in the space above the fuel pump - lots more than on my pug 306 hdi that's for sure ! i disconnected one of them that is definitely connected to the sensor and tested it with a meter, the resistance didn;t ever drop to 15 ohms that's for sure. I wasn't expecting to find a second, so did not even try to trace out for another once I'd found one !

Trouble is Citroen want 50 quid for the part and are claiming it is non refundable once ordered. I need to be sure I'm getting the right part for that !

I'll scan the picture they let me have in a while and post it here.

Tim

Post by **tmead** » 08 Jul 2010, 17:17

Many thanks, that's exactly what I needed to know. I thought there was a very faint click from inside the sensor.

Citroen are currenlty after 50 quid (plus vat) for this part in Cambridge.

I may just have a test with a sealed reed switch and a couple of resistors for the moment and see if I can get it to work. Nothing to lose as it's reporting as not working at present.

Tim

Post by **tmead** » 20 Jul 2010, 10:56

OK, I did it ! The combination of a non-refundable 50 quid quote and the worry that it might not be the right part anyway drove me to have a go ! I replaced the sensor with a reed switch from RS and a couple of resistors, all covered up with adhesive lined heatshrink.

Code Description Price
289-7806 Form C rectangular reed switch,CO 130Vac 5.30
683-2746 MRS16 Resistor A/P,0.4W,1%,15R 0.04
683-2730 MRS16 Resistor A/P,0.4W,1%,150K 0.04
481-1775 Blk adhesive lined heatshrink tube,3/1mm 2.96

Prices Ex VAT, and you'll need to buy 25 of each resistor at the grand price of a pound !

The switch only has about 6 inches of cable, so you need to solder it in place up under the wheelarch quite neatly, but it's pretty easy. The switch is held into place with three tie-wraps, and feels pretty secure so far.

I have some not very clear photos, but could send them to anyone contemplating a similar upgrade !

Tim

ej2095 · Post by **ej2095** » 22 May 2013, 20:31

Well 3 years later.. my fuel thingy thinks its also open..

n e one got n e pics?

Post by **tmead** » 22 May 2013, 22:20

Sorry, no pics. It definitely worked until I sold the car though !

Pug 307 recently showed cap fault, and hasn't returned after clearing. Might just be the Ecu gets its knickers in a knot if the cap isn't put on quite right ?

Tim

mikeC5 · Post by **mikeC5** » 14 Jul 2013, 11:35

tmead wrote:Sorry, no pics. It definitely worked until I sold the car though !

Pug 307 recently showed cap fault, and hasn't returned after clearing. Might just be the Ecu gets its knickers in a knot if the cap isn't put on quite right ?

Tim

Hi Tim - On my 05 Plate (MkII) 1.6HDi I have a push on - push off switch operated by the filler flap. As I have the dreaded " Possibility of particle filter blocking" message and read (somewhere) that this could be caused by the ECU not detecting the filler cap being opened/closed, I took the switch out. It has no lugs for wiring and nothing stuck to the base. I assume it's a magnet which then operates another switch, but where is the other switch/sensor? Any ideas?

Post by **tmead** » 14 Jul 2013, 23:35

Are you sure the thing you have is a switch? The C5 had a clicky thing that held the flap closed IIRC , but the switch was completely seperate and accessed from under the wheel arch. There was no to get to it from the filler flap.

Post by **tmead** » 14 Jul 2013, 23:43

Might be worth trying to find out if there's anyone local that can plug in and check. Lexis will give loads of info ! if your close to Cambridge you'd be welcome to pop round.

Tim

mikeC5 · Post by **mikeC5** » 15 Jul 2013, 12:20

Thanks Tim, I've found someone with a Lexis (Lexia?) who thinks that what I thought was the filler cap sensor might be something to do with the alarms (someone trying to nick fuel). Will get it checked this pm.

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