The 12-volt battery remains the leading cause of breakdowns recorded by the ADAC in its Pannenstatistik 2026. Tires, suspensions, and headlight adjustments account for failures during technical inspections. We observe that these issues all stem from neglected routine maintenance, rarely from a manufacturer defect. Understanding critical inspection points and methodically maintaining your car can prevent the majority of immobilizations.
12 V Battery and Charging Circuit: The Most Underestimated Breakdown Issue
A starter battery does not always give a warning before it fails. The capacity drop accelerates as the open-circuit voltage falls below a certain threshold, but the starter still turns. The driver detects nothing until the morning when the engine refuses to start.
We recommend a load test under amperage at least once a year, not just a simple voltage reading. A multimeter reading of 12.4 V says nothing about the actual condition of the plates. Only a conductance tester or a controlled discharge reveals the residual capacity.
On recent vehicles, the 12 V auxiliary battery also powers engine management units, electric power steering, and ADAS systems. A weakening battery can generate false fault codes in several control units without any battery warning light turning on. Before looking for a complex electronic issue, we systematically check the condition of the battery, its terminals, and its mounting.
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Tire Pressure and Technical Inspection: The 0.5 Bar Threshold
Since the technical instruction applicable on June 18, 2025, the technical inspection penalizes a pressure deviation of at least 0.5 bar from the manufacturer’s nominal value. This threshold applies to both over-inflation and under-inflation, and an imbalance between the two tires on the same axle falls under the same category.
The nominal pressure is listed on the label affixed to the driver’s door frame or in the fuel filler flap. It varies according to the load. A fully loaded vehicle (trunk, rear passengers) requires a higher pressure than the “empty” value indicated first.
We observe that the majority of drivers inflate their tires at the gas station without checking the manufacturer’s value, relying on an estimate. A poorly calibrated station gauge adds an additional margin of error. The result: pressures are often too low in the front, too high in the rear, leading to an unfavorable technical inspection on what seems like a trivial issue.
- Check the pressure when cold or after less than three kilometers of driving, never after a highway trip.
- Compare the measured value to the manufacturer’s plate, taking into account the vehicle’s load level.
- Visually inspect the sidewalls: a bulge, a deep cut, or asymmetric wear indicates a geometry or shock absorber issue, not just a tire problem.
Timing Belt: Manufacturer’s Replacement Interval and Warning Signals
The breakage of a timing belt usually causes a valve-piston contact that destroys the upper engine. The cost of preventive replacement is incomparable to that of engine failure. We regularly find belts that are overdue by several tens of thousands of kilometers, simply because the maintenance booklet was lost during a resale.
The replacement interval varies greatly from one manufacturer to another and from one engine type to another, even within the same brand. Relying on a general rule like “every 100,000 km” exposes you to errors. The only reliable reference is the manufacturer’s maintenance plan, which can be consulted through the network or in the vehicle’s technical documentation.
Beyond mileage, the age of the belt is as important as its wear. Rubber degrades through oxidation, even if the vehicle is driven little. A car that has traveled few kilometers in ten years poses a real risk of breakage. The tensioner pulley and water pump, driven by the same belt, should be replaced simultaneously.
Coolant and Air Conditioning Circuit: Two Often Confused Circuits
Coolant protects the engine from overheating and freezing. Its anti-corrosion properties diminish over time, accelerating internal oxidation of the engine block and radiator. We recommend checking not only the level but also the condition of the fluid: a brownish coolant or one loaded with particles should be drained, even if the level remains correct.
The air conditioning circuit operates on a different principle. The refrigerant circulates in a closed circuit, but micro-leaks at the connections and compressor lead to a gradual loss of charge. An air conditioning system that cools less does not always indicate a failure, sometimes it is simply a lack of gas accumulated over several years.
- The coolant level check is done with the engine cold, on the expansion tank, between the min and max marks.
- The air conditioning recharge requires a specialized station capable of measuring the exact amount of remaining fluid before reinjection.
- The cabin filter, often forgotten, conditions the quality of the air blown and the system’s performance. A clogged filter reduces airflow and overloads the fan.
Lights and Headlight Adjustment: A Common Reason for Re-inspection
Headlight adjustment is among the most frequently noted failures during technical inspections. A headlight that is too high dazzles oncoming traffic, while a headlight that is too low reduces the lighting distance. The adjustment shifts over time, due to vibrations and bulb replacements.
Checking the alignment of the lights takes less than five minutes facing a wall, with the vehicle on level ground, a few meters away. The cutoff of the low beam should form a clear horizontal line, slightly tilted down to the right. A visible vertical misalignment is enough to justify a visit to the workshop.
The condition of the rear lights and turn signals deserves the same attention. A burnt-out bulb often goes unnoticed by the driver, especially on reverse lights or the third brake light. A complete walk around the vehicle, with the lights on, remains the simplest verification gesture before a long trip or a technical inspection.
The average age of inspected vehicles reached 13.3 years in 2025. This aging fleet makes these checks all the more crucial: defects accumulate silently and only reveal themselves at the time of inspection or in an emergency situation on the road.
