Rev Counter

Mothman · Post by **Mothman** » Mon Jun 22, 2009 7:48 pm

Hi all,

rev counter on my non turbo L reg BX dosnt work, never has since i had the car, a common problem so i believe.
Is it an easy fix, do i need anything special, parts etc to repair it? Is it worth doing?
Since i sorted the cooling problems the motor has been performing very well, its getting more pleasurable to drive everytime i get behind the wheel.

DLM · Post by **DLM** » Mon Jun 22, 2009 8:46 pm

It's probably the sensor, if the rev counter connections are good at the back of the dash , and a pretty common fault.

If you're lucky the sensor could just be displaced from where it should be , if you're unlucky it's been damaged by contact with the flywheel. It's not exactly vital for a 19 diesel, though nice to have it working.

When BXs were common in scrapyards these sensors disappeared pretty quickly from scrap cars. Diesel Xantias may have the same arrangement as they have an XUD engine too - can anyone confirm? Otherwise it's a main dealer part - and probably expensive for what it is - if Citroen still do it .

toddao · Post by **toddao** » Mon Jun 22, 2009 9:23 pm

Where exactly is this sensor? And would it be the same for the Mk.1s? ( I want to investigate my non-working rev counter too!) I looked at the Service Citroen website and couldn't find anything available though I might have used the wrong wording.

DLM · Post by **DLM** » Tue Jun 23, 2009 12:53 am

On the Mark 2 diesels it sits in area of the engine bay that's normally pretty filthy, just round the corner at the back on the gearbox side of the engine.

Look to the left of the hydraulic pump. The lead for the sensor enters a cutaway at around the point where the engine block meets the gearbox bellhousing - after all, it's taking a feed from the flywheel as the teeth run past, if I understand the way it works correctly.

You should be able to see a fairly thick black wire leading into a cutaway, where the sensor head locates. The sensor's on a dogleg at the end of the wire. If I'm right, it's doing pretty much what an ABS sensor does.

RxBX · Post by **RxBX** » Tue Jun 23, 2009 1:11 am

Pug 205/309 XUD's also use the same sensor, but as there also getting thin on the ground now at the breakers yards !

Maybe early Citroen ZX's and Pug 306's XUD's could be a better source if there the same (but to be 100% sure, I'd have to take a look at the spare ZX 1.9TD engine I have).

I've had a look at my Xantia 1.9 TD and that looks like the plug end is different to the BX XUD unit and the wire is much thicker fully covered/sealed to the plug end and looks/feels like its manufactured from a Silicone type rubber !

It's also worth checking the condition of the three wires coming out of the sensor unit it self first, because these can fracture and cause an open circuit like-wise it's worth checking the other end of the wire (Brown-plug end) , if any of the wires are fractured just re-solder and use heat shrink sleeve tube to encapsulate the repair (Also check the wires of any donor unit for the condition of the wires).
When fitting a second hand unit remember that when you push the sensor tip onto the teeth of the flywheel starter ring (When engine is static of course) to pull it back approx. 0.50 to 0.75 mm (Air-gap) before nipping up the pinch bolt ! If you don't you'll likely to destroy the replacement unit on start up !

IIRC new sensor units have a couple of 'Pips' made from the same plastic moulding which is part of the sensor which set's the Airgap automatically when fitted hard up to the the teeth off the starter ring which is fitted to the flywheel and just wear off when the engine/flywheel starts to rotate on start up !

toddao wrote:Where exactly is this sensor? And would it be the same for the Mk.1s? ( I want to investigate my non-working rev counter too!)

The position of the sensor is approx. @ four/five o'clock position looking from the gearbox side of the engine towards the fly-wheel and under the HP pump area of the engine/gearbox flange joint.

Also IIRC all BX XUD units should have this sensor fitted as standard even if the car spec. does not have a Tachometer fitted as it's used as a garage/servicing 'Plug-in' for setting up of the engine's cold/hot rev's !

On vehicle's fitted without a tachometer the Brown coloured three pin plug is usually lurking around the front or back of the dipstick/filler neck (I'm not sure if the Brown plug position is the same on vehicle's fitted with a Tachometer).

(Todd, I would not think that a BX MK1 and MK2 XUD sensor would be any different, as the quality of this part couldn't be any worse IMHO for a MK1 versus a Mk2 but best to check with the main dealer)
Hope this may be of help !

Post by **mat_fenwick** » Tue Jun 23, 2009 9:52 am

I bought the sensor from a dealer in 2004, it cost about £17. I will try and dig out the part number if it helps.

If you follow the trailing grey lead on the left of the engine you will see its location, just above the turbo outlet flange.

DLM · Post by **DLM** » Tue Jun 23, 2009 12:02 pm

That's a lot clearer than my fumblings from memory - the last time I was head-down towards the r/h back of an XUD my attention was definitely on something else (and the green spray coming from it).

RxBX · Post by **RxBX** » Tue Jun 23, 2009 12:11 pm

Nice one Mat.
The sensor position look's more like it's @ the 5 o'clock position !
But it has been quite a while since I've been doing any spannering in that area on a vehicle fitted with an XUD (Thank god)

BTW it can be seen from the photo that the Grey shrouded wired sensor is the less robust design as to what I noticed fitted to my Xantia but I'd guess the sensor unit itself is basically identical and does the same job.

So a retro fit/mod, maybe a better option of a sensor from an Xantia (If there more easily available from a breaker's yard) with the BX brown plug nicely soldered on the end (That's of course if the plug's are different) and thus would make it more robust

jonathan_dyane · Post by **jonathan_dyane** » Tue Jun 23, 2009 2:28 pm

RxBX wrote: So a retro fit/mod, maybe a better option of a sensor from an Xantia (If there more easily available from a breaker's yard) with the BX brown plug nicely soldered on the end (That's of course if the plug's are different) and thus would make it more robust

Although, I have to say that I have found that if anything, Xantia rev counters tend to be more tempremental than on the BX...

Mothman · Post by **Mothman** » Tue Jun 23, 2009 8:44 pm

Hi again,

thanks for all your replies but ime afraid this one is too complicated for a simple mind like mine to understand. Havnt a clue where any wires are coming from behind and just down from the hydraulic pump, just been to look and seen several. Tugged at them both, did not understand whats what so will leave well alone and cope without the counter as ive done so for the last 3 years. As for taking the dash apart to check whether its fitted up correctly, well, ide rather crack open another tinnie.

Thanks again.

Andy

DLM · Post by **DLM** » Tue Jun 23, 2009 9:01 pm

As for taking the dash apart to check whether its fitted up correctly, well, ide rather crack open another tinnie.

It's very unlikely anyway as the sensor's the usual culprit. As you said, it's easy to live without one on a 1.9D - enjoy the tinnie(s).

Mothman · Post by **Mothman** » Tue Jun 23, 2009 9:04 pm

Thanks anyway bud,

i will drink all your health. A very helpful and pleasant forum whom to belong.

Andy