Speedometer sensor fault - Ford Focus Mk1

[alan_m]

Ford Focus Mk1, 2001, 1.6 Petrol

Whilst on holiday a couple of weeks back the speedometer became erratic
and then stopped working. No problem I thought - it had happened before
and at that time I did around 400 miles before replacing the speedometer
sensor. My Sat Nav was used as the speed indicator.

A hour of driving later, and just turning off a main road into a country
lane, the engine cut out completely with a slight smell of (electrical)
burning.

As it was getting dark and raining the car was recovered to a local
garage 5 minutes walk from where I was staying. The next day being a
Sunday, and the garage being closed, I decided to take a look at what
may be wrong. The 20A "engine" fuse had blown and on swapping it with
another fuse in the box I could start the car again BUT with a extremely
large amount of white 'electrical smoke'.

In the end I was in luck in that the fault turned out to be only the
speedometer sensor which had caught fire and melted. A new sensor, a
fuse and a total bill for just over £100 from the local garage got the
fault sorted and the car has done 500+ miles since without problems.

On my car the speedo sensor seem to last 70K miles and if it it happens
again I will definitely disconnect the wires to it the first sign of the
same problem. However, I don't think I will have the car the next time
it is due for failure :)

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[MrCheerful]

disconnection leads to other problems.

[alan_m]

On 24/08/2017 00:39, MrCheerful wrote:

>> On my car the speedo sensor seem to last 70K miles and if it it
>> happens again I will definitely disconnect the wires to it the first
>> sign of the same problem. However, I don't think I will have the car
>> the next time it is due for failure :)
>>
>
> disconnection leads to other problems.

On a previous failure where the sensor failed open circuit the other
problems were minor.

i) The speedometer/odometer didn't work.
ii) The engine warning light came on after around 20 miles
iii) At some constant speeds the engine was slightly lumpy/hesitant
iv) Possibly fuel consumption was higher

In general, the car started without problems, it pulled away without
problems and was very drivable - albeit possibly illegal without a
working speedometer (I used the Sat Nav speed report).

[Chris Whelan]

alan_m wrote:

>
> Ford Focus Mk1, 2001, 1.6 Petrol

[...]

> On my car the speedo sensor seem to last 70K miles and if it it happens
> again I will definitely disconnect the wires to it the first sign of the
> same problem. However, I don't think I will have the car the next time
> it is due for failure :)

I had a Mk1 '99 Focus for 10 years/100k. The VSS failed after a couple of
years, its replacement lasted.

I then had an '03 Focus in 2009. There was no evidence in the receipts that
came with it that the VSS had been changed, and I never changed it. I passed
the car on to a family member earlier this year, and he's had no problems.

It's my understanding that the design of the original VSS was improved
fairly early in production.

In all the VSS failures reported here and elsewhere, usual failure mode is
erratic speedo, then no output at all. I have never heard of one going short
circuit.

Was your replacement a genuine one, or non-OEM?

Chris


--
Remove prejudice to reply.

[MrCheerful]

the most dangerous problem is the engine dying as you pull up
momentarily/go to pull away (like when you pause in the middle of the
road waiting for a gap to turn right), coupled with the loss of power
steering. The radio going quiet at speed is annoying too:)