Winter wallets leave car owners cold in the cold, as Carly research shows glow plugs,coolant pumps and air quality sensors most likely to go wrong over winter
London, 22 January 2026 –
UK drivers could be facing repair bills of over £1,200 depending on the fault. Carly, the automotive diagnostics specialist, found the top three most common cold-weather failures could total up to £2,481 – a sum that could wipe out two months’ rent* for the average UK household. Based on insights drawn from more than 2.4 million diagnostic sessions between October and December 2025, Carly’s analysis highlights how cold-weather-related faults could add hundreds of pounds in unplanned repair costs for motorists, often striking during peak travel and holiday periods when household finances are already under pressure.
Analysing fault and repair data from UK users of its Carly OBD2 Scanner App – which enables drivers to identify, understand and resolve car issues, as well as calculate repair costs – Carly’s findings show that winter breakdowns are most commonly-linked to glow plug failures, auxiliary coolant pump failures and even faulty air quality sensors breaking down during the winter months.
Top winter car issues
Reasons triggering car issues and approximate repair cost
Probability of fault code
Glow Plug failure
Control unit defective = £848 – £1266
Glow plug defective = £618 – £835
Cable/plug defective = £116 – £160
Fuse /power supply defective = £56 – £76
60%
Auxiliary Coolant Pump failure
Pump defective = £570 – £820
Cable/plug defective = £116 – £160
Fuse defective = £56 – £76
65%
Air Quality Sensor failure
Sensor defective = £281 – £395
Cable/plug defective = £116 – £160
Fuse defective = £56 – £76
78%
Glow plug failure is one of the most frequently recorded winter issues, but it is important to note that glow plugs are only found in diesel engines. The most expensive repairs are linked to defective control units, typically costing between £848 and £1,266. Other common causes include defective glow plugs (£618–£835) and issues with cables or plugs (£116–£160), with fuse or power supply problems also occasionally reported (£56–£76). Overall, glow plug-related faults account for around 60% of the winter fault codes recorded.
Auxiliary coolant pump failure is another common winter problem, with a 65% probability of occurrence in the dataset. The most significant repair costs are associated with a defective pump, typically ranging from £570 to £820, while cable or plug faults and fuse issues tend to be less expensive to fix.
Faulty air quality sensors are the most prevalent issue recorded in the data, with a 78% probability of occurrence. Repair costs vary depending on the cause, with sensor replacement generally costing £281–£395, while cable/plug faults and fuse issues can range from £56–£160.
Commenting on the findings, Dali Ati, Head of Internationalisation at Carly, said: “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 bad for owners of diesel cars considering the cost range and likelihood of glow plug-related 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 on the road should have access to this type of information, helping them stay on top of potential issues as and when they arise.”
Carly’s findings suggest there is clear value in understanding the types of issues most likely to affect vehicles during winter. By identifying common faults early, drivers can better prepare their cars for colder conditions and reduce the risk of breakdowns and unexpected costs during some of the busiest periods of the year.
To support this, Carly offers a simple plug-in diagnostic solution that allows drivers to access professional-grade insights from their own vehicles. Available in two packages – Basic and Premium – Carly’s system connects via the OBD port to provide an overview of a vehicle’s health. Prices start from around £40.
View more about what Carly’s OBD solution can help drivers with here.
*Average rent is £1,146 per UK household for private renters, NimbleFins
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Automobile Magazine-UK
