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Ford Focus Saloon 1.8 (Zetec) MK1 - Speedo Needle Drops - kesher

Occasionally the speedo needle drops quickly to zero then returns immediately to its previous position. No power is lost and nothing else happens.

Sometimes a month or more could pass before I notice the needle drops again.

Ford Focus Saloon 1.8 (Zetec) MK1 - Speedo Needle Drops - hardway

Check the connector behind the dash pod.

'cours you have to pull the speedo/dash pod out first.

Ford Focus Saloon 1.8 (Zetec) MK1 - Speedo Needle Drops - elekie&a/c doctor
You need a new speed sensor in the gearbox.very common fault on Mk 1 focus.
Ford Focus Saloon 1.8 (Zetec) MK1 - Speedo Needle Drops - kesher

How difficult is it to replace the sensor. If I don't replace sensor will the speedo eventually stop working altogether?

How difficult is it to replace the sensor?

Ford Focus Saloon 1.8 (Zetec) MK1 - Speedo Needle Drops - elekie&a/c doctor
It depends which sensor you have . There are 2 types,one is a push fit with a lock pin.these can be a real pig to remove. The other type is a push fit with a screw,much easier to fit but the sensor costs a lot more.
Ford Focus Saloon 1.8 (Zetec) MK1 - Speedo Needle Drops - kesher

If I don't replace the sensor now. Will the sensor deteriorate further?