Since 1997, the Mercedes A Class has been a frequent site on our roads. Featuring a sub-compact, short wheel based design with the characteristic stylings from the German manufacturer, it has been a popular choice for drivers that want a luxury run-around. Like all vehicles, it’s not without its faults and issues, so what are some of the more common faults that you need to check for when considering purchasing a second hand A-Class?
And more importantly – which mean that you should avoid the purchase at all costs – and which are those that could be simply and easily cured with some new or used Mercedes A Class parts and a little mechanical knowledge?
Issues with the automatic gearbox in the Mercedes A-Class can often cause a significant loss of power, causing the car to switch into limp mode. This is often due to wear and tear on the car’s transmission system, or it could be triggered by a fault in the hydroelectric valve body.
It’s also worth noting that a poor weld on the dual clutch automatic gearbox of cars manufactured in October and November 2015 is prone to cracking, which can also lead to the car going into limp mode or the drive system failing completely. Check that the car is fully driveable and all gears can be accessed when out on the open road before committing to purchase.
DPF (Diesel Particulate Filter)
If the Mercedes A-Class you’re thinking of buying has been used for lots of short excursions, particularly around urban environments with restricted speed limits then the DPF can become clogged, causing the ECU light to illuminate on the dashboard.
If you think the car is a good price and the owner agrees, you could try to clear the DPF to find out if this is the issue. Drive the car out on the open road at around 2500rpm for over 10 minutes, and this should cause all the particles caught in the filter to burn away. If the ECU light still persists after this, you could try replacing the sensor before recommending the owner takes a trip to the mechanic.
When you’re out on a test drive, ensure that all the gears are functioning properly, especially when changing between first and second. There is a known fault with the axle drum that causes the gears to slip. If you have the mechanical skill, this can be an easy fix – if you’re prepared to risk purchasing the vehicle.
Rear Windscreen Washer
The A-Class is known for problems with the electrical systems. One place this reputation commonly manifests is in the windscreen washers. Both the front and back jets are known to be problematic, but issues with the rear jet are the easiest to solve. Check both the front and rear systems before buying any A-Class. If there are issues with the rear jets then this can be often solved by simply reattaching the hose. Front washer issues are more serious requiring you to replace the jets and hoses.
The boot catch is known to stick on the A-Class. It often starts off as a small niggle as the boot won’t open. Take care however, as this is often the first warning sign that a sudden failure is on the horizon. Try the lock before buying and be aware that any slight problem is probably going to cost you time and money should you end up completing the purchase.
Misfires in the A-Class are usually accompanied by the check engine light. This is because the usual suspect in this case is the ignition coil. When these coils fail, insufficient charge is delivered to the spark plugs and the air-fuel mix will not ignite. Keep an ear out on the engine when you’re out on the test drive for misfires.
There is a known fault in A-Class vehicles manufactured between September and November in 2014 where an issue with the installation of several fuses prevent the airbags from properly deploying. This issue is often accompanied by other electrical failures.
Models built between July and August in 2018 also suffer from airbag problems but for different reasons. A perforated edge on the dash can damage the airbag on deployment. Remember that you can also use the registration to find out if the vehicle needed a recall. If so, then check with the owner that any required work on the car has been completed.
Loss of Power
Loss of power seems to be a problem that has affected a couple of A Class production runs. Cars made up till 2013 suffered from an issue where the driveshaft sometimes detaches from the wheel hub, causing a loss of drive – fortunately the brakes and steering will still work. Some models made in 2015 suffer from a fragile camshaft which can cause loss of power. Again, definitely one to check out with the manufacturer if you’re considering buying a car from either period.
Leaking oil from a faulty O-Ring is a problem that is known to affect diesel versions of the A-Class manufactured in between February and November in 2014. If you leave this problem unattended it could damage the environment and leave your car low on oil – eventually causing knock on wear and tear to other engine components due to a lack of lubrication. Check under the car – or where the car has been parked to see if there are large patches of oil indicating a leak before you buy.
Clunking when Turning Right
When out on the test drive listen carefully for a clunking sound when turning right. This is not a good omen. Cars manufactured in 2015 are known to suffer from an issue with a bearing in the steering rack that causes a noise when turning right. If a bearing becomes damaged the chances are you will also have to replace the rear suspension, wheel bearings and the trailing arms too.
One of the major problems you might face with a Mercedes A-Class is a problem with the ECU, where it turns itself off the moment it comes on – or it simply becomes unresponsive. You’ll need to replace the unit to solve this issue. Always make sure that any vehicle you consider buying can be properly turned on before you buy.
Another weak point in the Mercedes A-Class is the starter motor. This is known to fail especially in older models with this electronic component wearing out. Should the car take a long time to start, or not start at all – then it’s probably worth avoiding for this common fault.
And Finally The A-Class is not a car that is by any means draped in glory. Over the years it has consistently performed badly when compared to its rivals, consistently appearing in the bottom half of surveys. The petrol model generally fares better than the diesel model – but both place badly when reviewed as a family car and a hatchback.