School-run queues on the A232 and what they do to charging
Term-time mornings around Nonsuch High School, Cheam High School and the local primaries mean a lot of Cheam cars do the same short loop twice a day, much of it queuing through the village crossroads on the A232. That kind of use is hard on the charging system. A cold start drains the battery, the engine then spends most of the trip at idle or low revs, and the car is switched off again before the alternator has put the charge back. Winter makes it worse, with lights and heater on for the whole trip.
On newer family cars with stop-start and smart charging, the car deliberately keeps the battery below full to save fuel and relies on the alternator to top it up when you lift off. On the quiet, slow roads by St Dunstan's Church and Lumley Chapel there's little chance for that to happen. If the alternator or its decoupler pulley is starting to fail, the first clues are usually a message saying stop-start is unavailable, or a battery that seems to need replacing far too often. Some owners go through two batteries before the real cause is found.
We look at the whole picture. The battery gets a proper health test, the alternator is checked under load, and we read the charging and battery management codes from the engine ECU. Where the car uses a battery sensor on the negative terminal, we check that too, because a faulty sensor can make a good alternator look bad. Only then do we give you a written quote, and the parts we fit are OE-specification, with a new belt.
The drive is straightforward: east on the A232 through Sutton to Carshalton, then north on the B277 to Hackbridge, or stay on the A232 to Wallington Green and turn up the A237. If the car is stuck on the drive, we can arrange collection. Our 3-month workmanship warranty covers the repair.