Ford Mondeo - Speedometer drops to Zero - once on every journey.

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Mon 10 May 2010 17:47
Ford Mondeo - Speedometer drops to Zero - once on every journey. - metchka

I have a Y reg. MK2 Mondeo Zetec-S. My speedo drops to zero after about 4 miles of driving, it then resumes normal operation after about another mile. The mileometer also stops, the car loses a little bit of power, and the volume of the radio suddenly drops.
My fuel warning light is NOT affected, and nor is the rev counter. Also, it is not an intermittent problem (i.e. probably not a loose or poor electrical or mechanical connection) because it happens JUST ONCE on every journey from cold, and always after about 4 miles of driving.

Any help would be appreciated. Many thanks.

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Thu 10 Jun 2010 12:08
Ford Mondeo - Speedometer drops to Zero - once on every journey. - mikej

The 'speedo dropping to zero' problem on a Focus is usually linked to a dodgy Vehicle Speed Sensor (vss) - could it be the same on a Mondeo ?

There are plenty of posts about this problem on this forum, including some of my own - trying searching for Ford Focus / vss or vehicle speed sensor.

If it is the vss, then replacing it is your only option - it's not an expensive part (~£30 for the Focus vss at least) but changing it can be difficult, particularly on older, higher mileage cars as the retaining pin can be very difficult to remove.

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Thu 10 Jun 2010 13:12
Ford Mondeo - Speedometer drops to Zero - once on every journey. - Collos25

Without doubt the speed sensor common fault or it could be the wiring .

Edited by Andy Bairsto on 10/06/2010 at 13:13

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Thu 10 Jun 2010 13:23
Ford Mondeo - Speedometer drops to Zero - once on every journey. - Lee1

Surely the slight loss of power and radio volume dropping is indicative of something more than just a loose speedo wire or dry solder? A momentary fault in the car's computer software program or electricity generation output due to either a software problem or bad electrical connection of some kind that changes at a certain engine or circuit temperature, perhaps?

(An amateur opinion, I'm not qualified.)

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Fri 11 Jun 2010 15:09
Ford Mondeo - Speedometer drops to Zero - once on every journey. - mikej

Surely the slight loss of power and radio volume dropping is indicative of something more than just a loose speedo wire or dry solder? A momentary fault in the car's computer software program or electricity generation output due to either a software problem or bad electrical connection of some kind that changes at a certain engine or circuit temperature, perhaps?

The vss talks to the ECU and when it develops a fault it can cause all sorts of problems, including the speedo dropping to zero, loss of mileometer reading, radio becoming quiet and (most worryingly) occasional total loss of power.

With a total loss of power, braking and steering become very difficult, so it's worth getting this sorted. This happened to my Focus on a few occasions.

If it is the vss in this case, then the fact that it only happens after 4 miles and once on each journey are likely to be red herrings.

It's probably wirth pointing out again that I am presuming that the Mondeo has a similar set-up to the Focus.

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Fri 11 Jun 2010 17:31
Ford Mondeo - Speedometer drops to Zero - once on every journey. - Lee1

Thank you for the reply.

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