COMPANY car breakdowns are set to reach record levels this year, but almost half of the cries for help to the RAC are due to wear and tear or human error. However, seven of the top 10 most common company car breakdowns require advanced diagnostic tools to identify the faults as a consequence of the dominance of on-board vehicle electronics increasingly contained within sealed engine management systems of new cars.

But that view was disputed by AA chief engineer David Lang, who said: 'The vast majority of breakdowns are caused by human error or wear and tear and diagnostic equipment is not needed. Engine management systems don't fail. It is the wires from them which fail and you don't need diagnostic tools for those either.'

But the RAC's fleet fault league table for the first six months of 1998 highlights the reliance by RAC patrols on a briefcase-sized diagnostics kit to identify almost 42,000 of the near 70,000 faults which make up the top 10 reasons for call-outs. With the top 10 faults accounting for 38.3% of all call-outs from company car drivers to the RAC, total fleet call-outs are now heading for a record 360,000 this year - up from 341,000 in 1997.

The trio of faults escaping diagnostic tool attention were: wheel changes, which replaced battery-related breakdowns last year as the number one reason for call-out and remains at number one in the first half of 1998 with 14,344 call-outs - 7.9% of all company car driver breakdown calls.

The AA does not publish a similar table of reasons for company car breakdown, but last month its 'Top 10 reasons for breakdowns' of all vehicles was headed by battery problems accounting for almost a fifth of call-outs.