Why does the cruise control on our Ford Fiesta fail intermittently?

My wife has a 2020 Fiesta Vignale (125) with 18,000 miles. She has a persistent problem with both cruise control and stop-start which often doesn't work. Despite having had a new battery fitted under warranty in June 2022 due to both not working, the problem reoccurs.

Her journeys are not short and normally comprise 80 mile round trips to Sheffield or 22 mile round trips to Mansfield. The main dealer says they can find no problem other than the battery not being sufficiently charged. Even with turning the aircon off on a journey the cruise control still fails.

Can you suggest any reason why this might be and possible solutions please?

Asked on 10 May 2023 by David Yates

Answered by David Ross
Although the dealer can only find an issue with the battery, the fact they say it is not sufficiently charged may indicate there is a problem with the alternator, as the journeys it is used for should be more than sufficient to charge the battery.

There could be other causes of the problem, including a parasitic drain on the battery, a damaged or faulty radar sensor, software or issues with the throttle and brake sensors. A more thorough investigation is required, so we would suggest either returning the car to the dealer or getting a second opinion from an independent Ford specialist.
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