AC system leak detection

Why leak detection before refilling?

An AC system that has lost refrigerant faster than the natural 10–15% per year almost always has a leak. If we simply top it up without finding the leak point, the new refrigerant leaks out again — maybe within weeks, maybe before the customer gets home. That's money down the drain and an unnecessary environmental burden: R134a has a GWP of 1430 and R1234yf has a GWP of 4, but even that low number doesn't matter if it just leaks out.

We therefore always recommend leak detection if your AC has stopped working in less than 4–5 years, or if the vacuum test during a regular service shows the system can't hold vacuum. It's the only way to know where the problem is and how big it is.

How we perform the leak search

We have two complementary methods and usually use both to be sure:

UV dye and UV lamp

First we add a fluorescent UV dye to the system along with refrigerant and oil. The dye circulates and sticks to every small leak point. After the car has been driven or the AC has run for a while, we shine a UV lamp on the system and look for the characteristic green-yellow fluorescent dots that reveal where it leaks. The method is very sensitive and finds even small diffusion leaks.

Nitrogen pressure test

We drain the system of refrigerant and fill it with dry nitrogen to 10–15 bar pressure. Nitrogen is inert (doesn't react with anything), dry and reveals leaks fast: we measure pressure drop over time, or use a gas sniffer to locate the actual point. On big leaks we often hear the hissing sound directly. Pressure testing is particularly good for finding leaks on the condenser, evaporator and pipe connections.

Common leak points

Experience from thousands of AC jobs shows that some points are more frequent than others:

• O-rings on pipe joints — the rubber dries out over time, especially where hoses meet aluminium
• The condenser in front of the radiator grille — exposed to stone chips and road salt, often corrodes from the outside
• The cabin evaporator — hardest and most expensive to replace because the dashboard has to come apart
• Compressor shaft and seals — wear parts that leak when the compressor has been idle for a long time
• Service ports — where we connect the service station, with their own seals that can fail
• Receiver-drier/accumulator — can corrode and leak after many years

Time and price

The diagnosis itself takes 30–60 minutes depending on whether we find the leak quickly or have to extend the search. The cost of the leak search is deducted if you book the repair with us afterwards — we just want the problem actually solved, not for you to pay twice for diagnosis and repair. If we find the leak in an easily accessible place (like an O-ring on a pipe), the repair can often be done the same day. For evaporator leaks we usually have to allocate more time — it can require 6–10 hours because the dashboard must be partially dismantled.

Book your AC service online or call us on 41 17 32 24.