Repairing a 24V truck radio: a technical guide for professionals
HGV car radios: diagnosis, repair and best workshop practices
In truck maintenance workshops, car radio breakdowns are frequent and often underestimated. Yet these multimedia systems manage much more than just the sound inside the truck: GPS navigation, voice commands, connectivity with driving aids, etc.
Rather than replacing this costly equipment, targeted repair is a reliable, economical and sustainable solution. Here's a practical guide for truck repair professionals. It will help you to understand 24V car radios, diagnose faults more easily and ensure efficient, cost-effective interventions.
Understanding how a 24V truck radio works
Unlike light vehicles, trucks operate on a 24V power supply. This calls for reinforced components: DC/DC converters, EMC shielding, thermal resistance (-40 to +85°C).
Advanced features on truck radios
Truck radios are no longer limited to broadcasting radio and sound into the cabin. They are now central digital interfaces that play an active part in the driving environment. Whatever the brand (MAN, DAF, Scania, Continental, VDO, etc.), these systems are designed to meet the specific requirements of long-distance drivers.
The most common truck features include :
- Multimedia playback FM/AM, DAB+, CD, USB, Bluetooth, mobile applications
- Smartphone connectivity : Android Auto / Apple CarPlay
- Truck GPS navigation : adapted routes, gauge alerts, OTA updates
- Driver assistance display (ADAS) cameras, guidance, panoramic vision
- Logistics interface : tachograph reading, multi-user synchronization, delivery mission
- Personalized profiles language, audio, driver preferences
- Integrated business applications fleet, document management, mission orders
This functional complexity means that each failure must be treated as a system problem, and not simply as an isolated fault. A complete diagnosis is therefore essential to avoid unnecessary replacements, pinpoint the source of the fault and guarantee the following a complete recommissioning of the system.
24V car radio: constraints to be aware of
From the point of view of on-board electronics, the difference between a light vehicle and a truck is its power supply voltage. To operate all its interior components, a truck needs a 24V power supply, unlike a car, which operates on 12V. Internal modules are therefore specifically designed to withstand this higher current requirement. This is the case for truck car radios, which are 24V multimedia modules, which distinguishes them from car radios.
However, some boxes in the cab of a truck are still powered by 12V. To ensure the electrical safety of these boxes, the truck is fitted with a DC/DC converter which transforms 12V current into 24V upstream of these specific electrical circuits. This is the case, for example, for powering smartphone charging sockets, the USB port or the cigarette lighter.
Truck multimedia loop: architecture, operation and technical constraints
A truck's 24V radio is part of a multimedia loop: an internal network that connects all the infotainment, navigation and driver assistance modules. This loop ensures the continuous flow of data between the various modules: screens, on-board computer, car radio, cameras, amplifiers or control interfaces. Depending on the features and options available on a truck, the multimedia loop varies from one model to another.
In a truck, this loop is based on high-speed communication protocols. These enable data to flow quickly and seamlessly. The different communication modes frequently used in a multimedia loop are :
- MOST (Media Oriented Systems Transport): protocol used on recent vehicles, usually equipped with GPS and/or ADAS cameras.
- CAN Bus (Controller Area Network): used for control functions such as volume or display adjustment
- Ethernet Automotive (BroadR-Reach): suitable for 360° cameras, driver assistance systems (ADAS), radar...
- LIN (Local Interconnect Network): reserved for simple management functions such as air conditioning or lighting.
Despite their reinforced design, 24V car radios for trucks can show signs of weakness, or electronic or software failures. Vibration, heat, humidity, electrical instabilities... all these factors put truck electronics to the test.
Here are the 5 most frequent breakdowns our teams encounter on truck multimedia systems, with symptoms to identify and the models most affected.
Truck radio breakdowns: how to identify them quickly?
Rigorous diagnosis saves time and avoids unnecessary replacement. Before sending a 24V car radio for repair, here are the key steps to follow directly in the workshop to ensure the source of the problem.
Why doesn't my 24V car radio light up at all?
Identifiable symptoms :
The total failure blocks the entire multimedia system. The car radio no longer lights up, there are no lights or displays, and no commands respond.
If the unit won’t start, even when the +APC ignition is switched on, and the button or steering wheel controls fail to activate, there may be several reasons for this.
Probable causes:
- 24V power supply fault or blown fuse
- Damaged electronic motherboard
- Software bug preventing boot-up
Models often affected by a complete breakdown: Renault Master and
MAN TGX or TGS head units
If you’re certain that the car radio in your truck has broken down, you can find a new set that’s compatible with the vehicle. But if you’re in any doubt about the model, the problem and you want to save money, you’re better off repairing the original unit. That way, you’ll keep the software and won’t have to reprogram the radio.
Why do I have a black screen on the truck's car radio, or does the screen get stuck on the logo at startup?
A black screen at start-up, a frozen image, absent backlighting or spurious lines often indicate a fault in the display system. In some cases, the sound remains functional, indicating that only the screen is affected.
Identifiable symptoms :
- Weak or no backlighting
- LCD screen failure
- Touch screen no longer works
- Screen stuck on brandlogo
- No display at all on startup
- Dead lines or pixels appear on the screen
Probable causes:
- Display power supply failure
- Communication problem between car radio unit and display
- LCD or LED display internal fault
- Problems with the liquid crystal display on a radio set
Model often affected by display problems: Mercedes Actros car radio
As you can see, a screen problem can be caused by the screen itself, or by an internal fault in the car radio. Rather than changing the truck’s screen without being sure of solving your problem, have both modules checked by specialized electronics technicians.
What should I do if the sound stops coming out or crackles in the truck?
Audio failures manifest themselves as a total absence of sound or crackling noises. They are common on truck car radios, and make it impossible to listen to music, the radio or even make phone calls over the air. Sound failure can be caused by a number of factors.
Identifiable symptoms :
- No sound at all, even at maximum volume.
- Intermittent sound or music that only comes out on one side
- Sizzling, sometimes accentuated when starting up or driving.
Probable causes:
- Integrated audio amplifier HS
- Fault in the power circuit or connection to the loudspeakers
- External audio module (in systems with remote amplifiers) damaged
- Altered sound output from car radio’s internal circuitry
Model frequently affected by sound loss : Mercedes Trucks car radio
In this case, you need to have the whole multimedia loop diagnosed by a professional: car radio, remote amplifiers, screen… Before doing so, don’t hesitate to check that the screen lights up properly, that the control buttons work or that Bluetooth is activated correctly.
Does the truck's car radio cut out at times or start up again and again?
Intermittent failures are typical of the truck environment: sound or display cuts out, buttons inactive at times. This type of failure particularly affects heavy trucks, which are subject to more vibrations or difficult driving conditions.
Identifiable symptoms :
- Random mutes of sound, display or controls
- Radio restarts while driving
- Increased malfunctions on rough roads or in cold weather
- Cuts become permanent over time
- Car radio occasionally switches off
- Functions start up for no reason, such as the CD player
Probable causes:
- Vibration-induced microcracks on welds
- Components weakened by temperature changes
- Humidity on electronic circuits
- Car radio programming problem
Untimely or intermittent breakdowns are the bane of every truck mechanic’s existence! They make diagnosis difficult, because the symptoms are not easy to reproduce in the workshop. At Repturn, we have the appropriate test benches to check radios under a variety of conditions: cold, hot, during vibrations, for several minutes… That’s why we advise you to go through our professionals to diagnose and repair the faulty multimedia module.
How to diagnose a faulty 24v truck radio? The 3-step guide
Rigorous diagnostics can save time and avoid unnecessary replacement. Before you send your 24V car radio for repair, here are the most important points to remember. key steps to be followed directly in the workshop to ensure the source of the problem.
Observe the symptoms before disassembling the car radio
Before plugging in a case or opening the unit, take the time toanalyze the car radio's behavior :
- Can you see that the screen is black or partially displayed?
- That the backlight is very dim?
- Display lights up but no sound comes out?
- Does GPS or Bluetooth work?
- Are the steering wheel controls active?
- If the screen remains frozen on the manufacturer's logo, does the sound still work?
- Can I perform an update if the car radio restarts in a loop?
- Does the display show an error message?
Ask yourself the right questions as soon as you start your diagnosis. All these signs may indicate an internal electronic fault: damaged motherboard, software bug, faulty power supplyetc. To make the repairer's work easier, please note all the symptoms you notice, so that we can identify the source of the fault more quickly.
Update your truck radio
If the car radio lights up and the screen is accessible, we advise you to try updating the radio. We recommend that you try updating your radio, car radio software bugs are common on trucks. Updating your car radio's software is essential for enjoying the latest features, correcting malfunctions and enhancing safety. Regular updates (or "reboots") ensure the performance and reliability of your vehicle's multimedia module. Before doing so, it's important to check which version is currently installed. This is usually done as follows:
- Hard to find: Car radios are not easy to identify. Their labels are full of part numbers, and we're never quite sure that the product we're looking for is the same as the original.
- Stocks are low: especially when it comes to truck radios. You can't always find the right model on the Internet, in a scrapyard or with a dealer.
- Rely on the warranty: A used car radio isn't always reliable and functional. But a repair at Repturn gives you a one-year warranty on your repaired part. A reassuring argument for getting back on the road and enjoying the music in your truck!
Depending on the manufacturer and model, updates can be carried out in various ways. Sometimes it's necessary to update the GPS, separately from the sound system or Bluetooth. In some cases, the software is available on the Internet and must be saved on a USB key or SD card for transfer to the car radio. For some brands, it is necessary to update the software directly from the manufacturer. In all cases, we advise you to refer to the manufacturer's manual to ensure a proper update.
Checking a radio's power supply, fuses and connectors
It's time to check your car radio's environment. Once disassembled, follow these 3 essential inspection steps:
Truck radio repair: why call on a specialist like Repturn?
The diagnosis is clear: the fault comes from one of the modules in the multimedia loop.
At this stage, attempting a "home-made" repair is not recommended and presents risks for the equipment. Replacing the car radio with a new part seems a good option, but new radios are expensive! As you can see, for us, the best option is still custom repair. We explain why.
Repair or replace: making an economic and strategic choice
It's time for us to present you, one by one, the arguments that lead us to believe that repair is THE solution for broken car radios.
- Reduce your maintenance costs: Radio sets are often very expensive when new. Particularly when they're truck-mounted and come with touch screens and options of all kinds. What's more, prices vary widely from one manufacturer to another. At Repturn, we've found that our services can save our customers up to 70% compared to buying a new part!
- Keeping the original radio : As explained above, the truck radio is not a stand-alone part. When you choose to have it repaired, you can be sure that all the parts are compatible with each other. By keeping the original car radio, you can be sure of being able to reassemble it identically, keeping the wiring harnesses and the truck's original interface.
- Reducing environmental impact: By upgrading the truck's module, you avoid having to produce a new part on the other side of the world. These systems are among the most resource-intensive in terms of the fossil fuels required for their manufacture (screens, electronic cards, components, plastics, etc.). What's more, you avoid throwing away a polluting component that's difficult to recycle, and which is undoubtedly repairable.
How about a used part to replace the broken car radio?
It's true that replacing a part with a used one is a reflex for many repairers. However, this option generates risks that we have measured for you:
Choose a service provider specializing in on-board electronics for trucks.
Repturn assists transport and commercial vehicle maintenance professionals with their on-board electronics needs. Dashboard, engine control unit, EBS, cockpit unit or multimedia system: our teams of electronics engineers are familiar with many references for 24V truck modules.
At Repturn, we don't just do functional repairs. We carry out complete refurbishment : inspection and repair of welds, replacement of faulty or fragile electronic components, replacement of screens, preventive maintenance on components likely to have weaknesses. Our aim is to return your equipment to you, reliable and ready to last.
Here are just a few of the advantages of our repair services:
- A one-year warranty on your repaired parts
- Dedicated support for professionals, from diagnosis to reassembly
- A customer area for making service requests and tracking them from A to Z
- A team of professionals specialized in on-board electronics for trucks
- An online repair catalog so you can find your information easily
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