Repair of Comand NTG4 Mercedes W204 / GLK – Gunshots in the speakers | 1-3 days

Last updated: 23.10.2025 (content)

The audio fault in Comand NTG4 has a fairly precise technical cause. A complete lack of sound most often results from a fault in the power-stabilising circuit. Loud crackles and “pops” are caused by a drop in voltage at the operational amplifiers, the circuits responsible for processing the audio signal. This in turn leads to sudden discharge of the coupling capacitors.

You get into your Mercedes W204, set off, switch on the radio and suddenly deafening crackles come from the speakers. The sound can be so loud and so unexpected that it is easy to be startled, especially while driving.

Another time, after a short stop at a filling station, you start the car and instead of music you only hear rhythmic “clicking” or “popcorn popping”. The screen works, the navigation shows the map, but there is still no sound. In practice, the Comand system becomes useless and clearly reduces driving comfort.

In this article we show why Comand NTG4 fails in exactly this way and what its effective refurbishment looks like (repair usually takes 1-3 working days, you receive a 24-month warranty, and the total cost is 1476 zł incl. VAT).

Before you start looking for a risky used unit (which may fail just as quickly) or hear the price of a new unit at the dealer, which can be shocking (even 9,000–17,000 zł), it is worth pausing for a moment. This fault is 100% repairable.

How do you identify Comand NTG4 navigation?

Check two distinctive features: an automatically retracting screen in the centre of the dashboard and a PCMCIA card slot on the front panel.

Your Mercedes (C-Class W204 from 2007-2010 or GLK X204) is equipped with the Comand NTG4 system if it has:

1. Retractable screen

This is the most obvious feature. When the ignition is switched on, the large colour screen automatically rises from the upper part of the dashboard.

2. PCMCIA slot

Look at the front panel of the radio, where you insert the disc. Below the largest knob marked “ON” there is a rectangular slot for PCMCIA memory cards. This is a characteristic slot you will not find in the lower radio versions.

Label details

If you already have the radio removed, you will find the markings “Head Unit High ECE Single” or “Head Unit High ECE Changer” on the label on top of the casing. It is this radio, the central radio module, that is made by Mitsubishi.

Fault symptoms – “machine-gun fire” and no sound

The most common symptoms are sudden, very loud crackles or complete loss of sound, apart from the characteristic “clicking”. It is worth noting that the problem almost always appears only after the radio has warmed up, usually after a few minutes of driving or after restarting the car.

If you recognise any of the scenarios below, then in practice it is 99% this fault we are describing.

1. Loud crackles, pops and knocks from the speakers

This is by far the most troublesome symptom. Very loud and irritating noises suddenly start coming from the speakers, with no warning at all.

• What it sounds like (customer descriptions): Customers most often describe it as a “machine-gun pop”, “otherworldly snorts”, “popcorn popping sounds”, “rhythmic knocking” or simply “knocks”.
• When: Usually after the radio has warmed up. In winter, or simply on colder days, the problem may occur less often.
• Consequence: Such noise is practically unbearable and can be very alarming while driving. The only thing that really helps is to switch the radio off immediately with the button.

2. Complete loss of sound (with the screen working)

The radio switches on, but instead of music you hear silence or only quiet “clicking”.

• Context: At the same time the screen extends correctly, the navigation shows the map, and the phone connects via Bluetooth. In other words, everything seems to be working properly, except for the audio path, i.e. the section responsible for sound.
• When: The problem usually appears after restarting a warmed-up car. Customers describe it as a “city driving scenario” — it works in the morning, but after 5 restarts in 20 minutes the sound disappears.
• How it disappears: The problem only goes away once the car has completely cooled down, for example after an hour parked or the next morning.

3. Strange noises with the car... switched off

Some customers report that these anomalies, such as knocking or squealing, can appear even when the car is locked and the audio system remains completely switched off.

4. Other Comand NTG4 faults (which we also repair)

Although this article focuses on audio, these units also suffer from other faults, which we also refurbish:

• Navigation keeps resetting
• Freezing on the Mercedes-Benz logo
• The system fails to boot at all, resulting in a black screen

If you recognise any of these symptoms, it is worth noting that delaying usually only makes matters worse. This is a typical hardware fault, which we eliminate for good.

Main causes of the fault – why does the radio fail after warming up?

The cause is natural wear, in other words ageing of the electronic components in the audio path. Once warmed up, these parts lose their characteristics, which means unstable voltages and interference appear, in other words crackling in the speakers.

1. Ageing components (end of life)

Comand NTG4 units were fitted from 2007 to 2011. The electronic components in the audio path were designed for a few years of use, not a dozen. They simply age over time.

2. Temperature influence (the main culprit)

Over the years, and under the influence of constant temperature changes, that is heating up during operation and cooling down while parked, these components lose their original properties. In practice, this means, for example, a change in resistance or capacitance.

• When the radio is cold, for example in the morning, the components are still briefly “holding” their values and everything works properly.
• When the radio warms up, the components lose stability, which leads to a “difference in potential”, that is an electrical imbalance, and to unstable control voltages in the audio path.

It is these sudden voltage spikes that you then hear as worrying pops and crackles in the speakers. It is worth noting that the source of the problem is not software-related, so a software update alone will not solve anything here.

Repair process step by step

The whole process is straightforward and usually takes 1-3 working days in total. You send just the radio, meaning the radio itself without the screen, and we carry out diagnostics, replace the faulty components with new ones, test the unit in car-like conditions and send it back with a 2-year warranty.

1. Contact and shipping

At the start, the customer contacts us to arrange a date. They then deliver the unit in person, by post or by courier.

• IMPORTANT: It is worth sending just the Comand unit itself. There is no need to remove and return the display (LCD), that is the screen, because we have the relevant test looms and our own screens at the diagnostic bench.

2. Diagnostics and your decision (1-2 days)

Once we receive the radio, we carry out the key test described in detail below to confirm the fault, namely the characteristic pops and crackles. Whatever the result, we contact you, confirm the fixed repair cost (1476 zł incl. VAT) and wait for your approval before starting further work.

3. Repair (within 1-3 days)

Once approved, we begin the refurbishment. We do not “heat up” old circuits. Our repair involves replacing the faulty audio-path components, that is the elements responsible for sound processing, with brand-new parts with greater durability. In practice, this is the stage that permanently removes the source of the problem.

4. Testing and return shipment

After repair, the unit undergoes full load and temperature testing. We then return the working radio to the customer, included in the service price, together with a written 24-month warranty (VAT invoice).

How do we test equipment? (Our test bench)

Our specialist test bench faithfully simulates the environment of your Mercedes (W204/GLK), giving us 100% confidence that the fault has been permanently removed.

You often ask how we can diagnose a radio outside the car. To run Comand NTG4 on the bench, we connect all the necessary components to it:

• Original display
• Controller, that is the centre console control unit
• Ignition-on signal from the ignition switch
• Speaker system
• CAN bus, that is the car’s communication network, for full communication
• Power supply

This set-up allows us to do two key things:

1. Before repair: confirm the fault is present 100%. In practice, we deliberately test the unit under load to provoke crackling.
2. After repair: carry out full testing so we can be sure the problem will not return.

What if the problem is the amplifier, not the radio?

In around 90% of cases, the Comand unit is to blame. However, if you are unsure, for example if you have a Harman Kardon system, we can check that too.

1. Start with the radio

In around 90% of cases, the main unit Comand NTG4 is responsible for the popping and crackling. That is why it is worth starting diagnostics by checking it first.

2. Not sure what you have in the car? Check the VIN

If you are not sure whether your car has an additional amplifier, for example Harman Kardon, send us your vehicle VIN number. We will check the vehicle’s factory configuration free of charge and advise which part is worth removing and sending in.

3. Amplifier repair

If it turns out that your Comand radio is working properly and the fault lies in the amplifier, we can repair that too.

Price, turnaround time and warranty

The repair costs 1476 zł incl. VAT, takes 1-3 working days, and you get a 24-month written warranty as part of the package.

Price details

What is included in the price:

• Full diagnostics on the test bench, i.e. under controlled conditions, including temperature tests
• Replacement of damaged audio path components, that is the parts responsible for sound, with brand-new factory parts
• Full load tests after repair, in other words checking how the unit performs under heavier load
• Written warranty for 24 months
• Return shipping to the customer

Refurbishment vs used unit vs new from the authorised dealer

In practice, refurbishment turns out to be the most sensible solution. It provides a lasting result, unlike a used unit, while still remaining reasonably priced, especially compared with buying a new unit from the authorised dealer.

1. Risk of buying a used unit

Buying a used Comand NTG4 unit for 1500-2000 zł is, in practice, a lottery. Such a unit usually comes from a car of the same age, i.e. from 2007-2011, so it is almost certain to have the same component fault. A crackling issue may appear shortly after installation, unless it is not already present. It is worth remembering that we are talking about technology that is already over a dozen years old, and one of the stages in the development of Mercedes-Benz multimedia systems.

2. Authorised dealer cost

A new unit from the authorised dealer, that is from an authorised dealer, can cost a great deal, even 17,000 zł. This means that in many cases the expense exceeds 30-50% of the value of the entire vehicle.

3. Refurbishment (our choice)

You pay 1476 zł and receive equipment with new, durable audio components and a 2-year warranty. In practice, it is a solution that is clearly more durable than a used unit and many times cheaper than a repair at the authorised dealer.

Have another question? It’s worth checking whether the answer is already in the faq. If not, get in touch with us.

About the author of this article

The article was prepared by the workshop's technical team. We specialise in advanced diagnostics and repair of factory radio and navigation systems from premium brands, including repair of Mitsubishi products made for Mercedes-Benz. We have many years of experience and have repaired hundreds of Comand NTG4 units fitted in Mercedes Benz cars.

Get the sound back in your Mercedes – book a repair

There’s no point driving in silence any longer, or risking a heart attack every time the speaker goes “bang”.

No more frustration. We offer lasting refurbishment of your Comand NTG4 unit.
The process is simple: you pack it, send it to us, we repair it, and you get back fully working equipment with a 2-year warranty.
The whole service costs 1476 zł incl. VAT, and turnaround time is 1-3 working days.