Ask the Mechanic: Why does my car battery get drained overnight?

Hello Paul, I would like to know why my battery is draining overnight. I have to jump start my SUV in the morning and although it runs smoothly during the day, the moment I turn it off, it is back to jump starting the following morning.


Hello Joan, there are a few reasons why a battery will drain overnight. Ordinarily, a car battery serves to start your car engine, which in turn uses an alternator to charge the battery and restore the recommended charge power capacity as you drive. Here are some common causes of battery drain:

1. Forgetting your headlights on. Whereas many car models will switch off the headlights as soon as the ignition switch is turned off, a few others will not.

2. Parasitic draw. Most new cars on our roads such as yours will have electrical components that keep running even when you switch the ignition off. These include the security system, clock, memory function of the engine management computer and other control modules. These features will not drain the battery much but when faulty, they can draw more power than they should. Also, faulty components such as glove box lights, seat adjustment switches, radios or electrical door locks with short circuits or bad relay switches can fail to stop running, which will drain the battery overnight. A good electrician will be able to identify the parasitic draw.

3. A faulty battery which is old, damaged or weak may not hold charge overnight.

4. Loose or corroded battery terminals will not allow the battery to get fully charged as you drive around.

5. A bad alternator. Ordinarily, a good alternator charge should range between 13.7 and 14.3 volts of direct current (DC) charge. This is sufficient to charge your battery fully in order to hold enough capacity overnight or start your car after a number of days of storage. If the alternator is damaged and does not provide sufficient charge, the battery will drain completely during overnight parking.

6. Short drives. Starting your car takes a lot of battery charge. Ordinarily, the alternator restores this charge as you drive. If you make frequent short journeys with prolonged stops, the alternator does not have enough time to fully charge your battery. This is worsened by the age of the battery with older batteries being more affected.


Hello Paul, I drive a Mercedes C230 2.5 litre with a V6 engine with 90,000km. Lately, the engine check light comes on in the evening and goes away the next day. Each time it comes on, the car appears to have too much power. A technician’s scanned it on two occasions with code P00012 and eventually advised that the balance shaft kit with four camshaft gears are needed. This is an expensive job and a second professional opinion would come in handy.


Hello Dorrin, the diagnostic fault code on your Mercedes is DTC P0012 ‘A’ camshaft position timing over retarded Bank 1. Presence of this fault justifies the mechanic’s suggestion to replace the balancer shaft kit, which should come with the camshaft solenoids. In addition, the timing chains should be inspected for ageing or slackening and replaced where necessary. Presence of the above fault code most likely indicates a mechanical fault in the timing system.

Your car falls in the range of Mercedes engines that had a recall because of failing balancer shaft gear teeth. This tends to cause a retardation or advancement of engine timing as well as failure of the camshaft variable valve timing function of prompt adjustment of engine intake valve lift. This alters engine performance and fuel economy, a likely cause of the erratic performance you describe.

The engine must lifted out of the car to access the timing case area. Then, the mechanic should replace these components as well as properly time the engine.

Yes, it is a delicate and costly job but it must be done to avoid further damage to the engine valves and pistons due to faulty timing.


Hello Paul, I would like to know if there is any car brand that has the same similarities to the Toyota corolla for both cheap spare parts and maintenance. 


Hello Isaac, the Toyota Corolla has always had affordable fierce rivals on the global car market such as Nissan’s Datsun Sunny, Honda’s Civic, Volkswagen Beetle, Mitsubishi Lancer and lately, the Korean Kia. The Toyota Corolla was launched as a sub-compact car in 1966 and has remained one of the best selling cars in the Toyota stables. It was positioned as a practical and affordable sub compact (not too small and not too big) transport solution.

Toyota has over the years built different body shapes of Corolla such as sedans and hatchbacks to meet the unique taste and needs of car buyers. Popular Corolla models over the years have included the sporty Levin and Sprinter, the practical station wagons such as the Fielder, subcompact saloons such as the Axio and mini wagon concept such as the Spacio. These different name plates have catered for different buyer needs.

Toyota endeavoured to make Corolla appeal to its customers with practicality of design (seating and loading space) as well as affordable running (fuel economy) and maintenance cost. Here in Uganda, the Corolla’s popularity has over the years been based on availability of cheap to buy used Corolla models such as Spacio, Axio and Fielder, among others with affordable new and used spare parts. Nissan has put up fierce competition in Uganda over the decades with its renowned tough reliable Datsun, Sunny, Sentra and Pulsar.

These have been Corolla’s closest rivals on the local car scene because they have tried to meet the practical and economy (affordability) attributes that attract many Ugandan used car buyers.

The brand new car segment has mixed fortunes as new entrants or disruptors such as the Korean Kia have challenged the Corolla supremacy in terms of quality, technology, practicality and affordability for both ownership and maintenance cost.


Hello Paul, why doesn’t my fuel system bypass fuel correctly? I have changed the fuel regulator, fuel injectors, fuel pump and filter and every time I turn my truck on with starter fluid in TBI, it bogs out and dies after 15 seconds. I have checked the fuel pressure and it is good at 11 psi. Also, I am only getting fuel to pass through my left injector but no fuel spits out of the right injector.


Hello Daniel you need to check your truck’s engine management system, which delivers electrical signals that activate fuel injectors during a fuel delivery cycle. From what you describe, you have overhauled the entire fuel system but some fuel injectors are not delivering fuel. A computer diagnosis will quickly reveal whether there is a circuit issue with the fuel injectors in question.

A good car electrician can be able to check connectors, circuits or the engine control module to determine the cause of breakdown. Forceful induction of starter fluid through the air intake provides a short term start solution that is not sustainable as there is no sufficient fuel supply to all cylinders. Resolve the circuit break down to the said fuel injectors.

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