A hidden crash repair isn't always visible. How the paint thickness gauge, used in a used car inspection, exposes repairs to the bodywork.
A car that has been in an accident and properly repaired isn’t necessarily a bad buy. The problem starts when the accident is hidden: you pay the price of an accident-free car, while you may be buying one with a compromised structure, worse behaviour in a new collision and a lower resale value. The paint thickness gauge is the tool that brings that kind of work to light, and below we explain how it works.
In the Greek market, where many used cars have had more than one owner or were imported from abroad, the seller often doesn’t know the full history of the bodywork themselves. The measurement doesn’t rely on what anyone remembers, but on what is left on the metal.
What a paint thickness gauge measures
A paint thickness gauge measures, in microns (thousandths of a millimetre), the thickness of the layers on top of the metal: primer, colour and clear coat. It is placed on the surface of the body and gives a reading in a second, without leaving any mark.
The logic is simple. At the factory, every car is painted by an automated process, so the thickness is roughly the same on every panel. When a panel is repainted at a body shop, new layers are added and the thickness goes up. When a panel has been dented and filled with body filler, the reading goes up even more.
What the readings mean
The values vary by manufacturer, model and colour, so there is no single number that applies to every car. As a general guide:
- Roughly 80 to 180 microns: the usual range for factory paint on most cars.
- Roughly 200 to 300 microns: possible repainting, for example after a scratch or wear.
- Over 300 microns, and especially much higher: usually filler, meaning a panel repair after an impact.
- Very low readings in one spot: may mean the panel has been heavily sanded or polished, or that it has been replaced.
More important than the absolute value is the comparison. We measure each panel at several points and compare it with its neighbours and with the matching panel on the other side. If the front left door reads 110 and the front right reads 290, something has happened on the right side, whatever the model’s factory range.
Aluminium, plastics and composites
Many modern cars have aluminium bonnets, doors or wings, while bumpers are plastic. Basic gauges only measure on steel. A professional instrument also recognises aluminium, so the measurement isn’t “lost” on those panels.
On plastic parts the gauge doesn’t measure. There the check is visual: a difference in shade, “orange peel” in the paint, traces of masking tape or paint overspray on the rubber seals and grilles.
The points we measure in a used car inspection
In a full bodywork check we systematically measure every exterior panel:
- the bonnet, the roof and the boot lid or tailgate,
- the four wings and the doors, at several points each,
- the pillars and the sills, where a repair often points to a more serious impact,
- the edges around the wheel arches.
The readings are recorded and go into the written report, so you know exactly which panel has been repaired and how much.
Repainting doesn’t always mean a crash
A sign of repainting isn’t automatically bad news. Many owners repaint a bumper or a door after a scrape in a car park, or a bonnet peppered by stone chips. These are cosmetic repairs that don’t affect the car’s structure.
What we look for is the pattern. Repainting on a single panel is common. Repainting and filler on the wing, door and pillar of the same side, together with uneven gaps, is a sign of a collision that deserves a closer look.
What else we check to confirm
The gauge shows where there has been work, not always how serious it was. That is why we combine the measurement with:
- The gaps between panels: doors, bonnet and wings should have even, parallel gaps.
- Bolts and hinges: spanner marks show that a panel has been removed or replaced.
- Labels and markings: factory labels on pillars and under the bonnet are often missing or painted over after a repair.
- The underside and mounting points: pulling marks on the chassis or welding traces in the engine bay point to a more serious repair.
- The glass: different manufacturing dates or brands on the windows can mean replacement.
The bodywork check and the all-round body inspection are already included in the Basic Inspection. In the Full Inspection the car also goes up on a lift to check the underside and the chassis. See what each used car inspection package covers.
How to use the findings
If the seller told you the car is “accident-free” and the readings show filler on three panels, you have two options: walk away, or negotiate on the evidence. A cosmetic repaint usually justifies a small discount. A structural repair changes the car’s value completely. In our article on how to negotiate the price with evidence we explain how to present the findings without souring the conversation.
An example from practice
On a five-year-old family SUV advertised as “accident-free, one owner”, the readings on the left side were all in the same range as the roof and bonnet. On the right side, the rear door and rear wing showed several times the thickness of the rest, and the pillar between them was also high. Underneath, the sill on the same side had signs of straightening.
The pattern pointed to a side impact repaired at a body shop, not a simple repaint. When the findings were put to the owner, they remembered that “someone had bumped it in a car park”. The buyer now had the evidence to decide: walk away, or negotiate a price that matched a repaired car.
Can I do it myself?
Cheap paint gauges are on sale, and they are better than nothing. The hard part, though, isn’t the measurement but the interpretation: what is normal for that particular model, which panel is aluminium, and which combination of findings points to a serious collision. Experience from hundreds of inspections makes the difference.
What to do before the measurement
A little preparation helps get reliable results. Ask for the car to be clean, but not freshly detailed with a thick layer of wax, and in a spot with good light, ideally daylight. Ask the seller whether they know of any repairs or repainting; their answer will be compared with the readings and tell you a lot about their honesty. If they have body shop invoices, ask to see them: a documented repair at an authorised workshop is a very different matter from a hidden one.
Conclusion
The paint thickness gauge leaves no room for “accident-free” cars that aren’t. Together with a visual inspection and a check of the underside, it gives a clear picture of the car’s past. If you are thinking of buying a used car, also see our guide to 10 things to check before buying a used car, or book an inspection wherever the car is, anywhere in Attica.
Frequently asked questions
Can the paint gauge damage the paint?
No. The measurement is made by simple contact and leaves no mark at all.
Is a car with repainted panels a bad buy?
Not necessarily. A proper cosmetic repaint is common. What matters is the extent of the repair, whether it involves the structure, and whether you were told the truth.
How long does the measurement take?
A few minutes for the whole body. Interpreting the results and combining them with the other findings is what takes experience.
Is paint measurement part of the CarCheck used car inspection?
Yes. The bodywork check with a paint thickness gauge is already included in the Basic Inspection, which is carried out on site anywhere in Attica. Book online.
