London, 22 January 2026 – As temperatures drop across the UK, motorists could be staring at winter repair bills of over £1,200, according to new research from automotive diagnostics specialist Carly. The analysis of more than 2.4 million diagnostic sessions between October and December 2025 highlights how cold-weather faults could hit drivers’ finances hard, particularly during peak travel and holiday periods.
Carly’s findings show that glow plug failures, auxiliary coolant pump issues, and faulty air quality sensors are the most common winter breakdowns, with repair costs for each potentially wiping out two months’ rent for the average UK household.
Glow Plugs: Diesel Drivers Beware
Glow plug failures are among the most frequently recorded winter faults, but they are limited to diesel engines. Carly’s data shows that defective control units—responsible for managing glow plug operation—carry the highest repair costs, ranging from £848 to £1,266. Other causes include worn-out glow plugs themselves (£618–£835), cable or plug issues (£116–£160), and occasional fuse or power supply failures (£56–£76). Overall, glow plug-related faults accounted for around 60% of winter fault codes recorded in Carly’s dataset.
Auxiliary Coolant Pumps: Cold Can Stop the Flow
Auxiliary coolant pump failure is another common winter headache, occurring in around 65% of fault reports. Repair costs can be significant when the pump itself is defective (£570–£820), although cable or plug issues and fuse failures are typically less expensive to resolve. Failure of the coolant pump can lead to overheating or inadequate engine warming, compounding problems in sub-zero conditions.
Air Quality Sensors: Small Sensors, Big Costs
Faulty air quality sensors are the most prevalent winter problem, showing up in 78% of cases analysed. While the sensors themselves generally cost £281–£395 to replace, wiring or fuse issues can range from £56–£160. Malfunctioning sensors can affect vehicle performance and emissions, making timely detection and repair crucial during colder months when engines are under additional strain.
Insight and Preparation Are Key
Dali Ati, Head of Internationalisation at Carly, commented: “Winter breakdowns remain a significant and costly issue for UK drivers. Our data shows that some of the most common faults reported during colder months—particularly for diesel owners facing glow plug failures—can also be among the most expensive to fix. With better visibility of vehicle health, drivers can prepare more effectively and avoid being caught out by unexpected repair bills. At Carly, we believe that all drivers should have access to this type of information, helping them stay on top of potential issues as they arise.”
Carly’s analysis underlines the value of early detection. By understanding the faults most likely to affect vehicles during winter, drivers can take steps to prepare their cars for colder conditions, reducing the risk of breakdowns and unplanned costs.
To assist motorists, Carly offers a simple plug-in diagnostic solution. Connecting via the OBD port, the Carly system provides professional-grade insights into a vehicle’s health. Available in Basic and Premium packages, prices start from around £40, offering an accessible way for drivers to stay ahead of costly winter repairs.
