Intermittent speedometer

[fastred]

The speedo on my V6 Xantia Mk2 has begun to periodically drop to zero irrespective of the car speed, and at the same time the mileometer ceases to work. Tapping or even thumping the dial has no effect, and the fault appears entirely random, and when it does start to work again it behaves perfectly. I would estimate that the problem occurs roughly 5% of the time at the moment. Seems very like an electrical fault somewhere , not a sticking one. My wife reports seeing the needle drop suddenly to zero from 60mph and them jump back into action again 2 or 3 minutes later.

Anyone got any hints as to where to start looking for a fault, preferably without having to remove the dash first.
TIA

fastred


Xantia 2000 V6 Exclusive.

[CitroJim]

I think the dash may be the wrong place to look actually. I'd begin my look at the vehicle speed sensor in the gearbox. It feeds its signals to three other places besides the speedo, the Engine ECU, the Autobox ECU and the suspension ECU. A Lexia check of live data will show if it is this sensor as the signal to all the ECUs will fail at once and together.

The good news is that the sensor is dead easy to get at, being mounted in the same place as on any manual gearbox, that's on the RH diff housing. Also, the sensors are the same as those fitted to manual gearboxes.

I would check the connector as it's in a nicely exposed spot for oily muck and coolant leaks.

[fastred]

Thanks Jim. I will try giving the connectors a good clean.
fastred

[f00lzz]

I noticed that at the same time the speedo stops working the suspension also goes very hard

[CitroJim]

I noticed that at the same time the speedo stops working the suspension also goes very hard

That's a good sign it's the VSS then as the Hydractive ECU will be loosing the speed signal and will get all confused. A Lexia diagnosis should show a stored fault to this effect..