What are cold water shock tests and why do they matter ? Cold water shock tests (often called an ice water shock test) reproduce what happens when very cold water suddenly contacts a hot automotive component. Think of driving on a winter road, then hitting a puddle: rapid quenching can crack housings, compromise seals, or distort connectors. The goal is to verify mechanical integrity, sealing, and functional performance after this thermal shock event as defined in ISO 16750-4.

If your components live in splash zones or can encounter water crossings, cold water shock tests – both splash water test and submersion test – are critical sign-off items. Building a precise test plan against ISO 16750-4, and mapping to VW 80000 and MBN LV 124 K-12 where applicable, will keep you aligned with customer expectations and reduce late-program surprises. Terminology note: “Cold water shock test” and “ice water shock test” are used interchangeably in labs and specs. ISO uses “cold/ice water” language to indicate near-freezing water, not frozen solids.

Cold water is jetted/splashed over a pre-heated DUT (device under test). This simulates puddle splash or wheel spray impinging on a hot part located in a splash zone (engine compartment, underbody).	Splash Water Test
The pre-heated DUT is immersed into cold water. This represents deeper water crossings or localized flooding where a hot component is dunked.	Submersion Test

The purpose of the test is to simulate the thermal shock induced by cold water splashing over a hot system/component. This happens when driving on wet roads in winter and applies to products in the splash areas of the vehicle.The failure modes are a mechanical cracking of materials or seal failures caused by different temperature expansion coefficients.Additional failure modes not addressed in 5.3.2.1 are loss of tightness and/or intrusion of water into the system/component.		5.4.1 Purpose	5.4 Cold water shock tests｜ISO 16750-4
There are two possible methods to perform this test (see 5.4.2 and 5.4.3).For all components mounted over the fording depth,the submersion test can be skipped. Note: This is not a corrosion test.
The DUT shall be tested with the following procedure as one cycle.The procedure of c)and g)and transfer time (ty and trp in Figure 8)may be skipped in case ofusing one single chamber with both heating and splashing.	5.4.2.1 Test method	5.4.2 Splash water test
a)Place the DUT with operating mode 1.2 as defined in ISO 16750-1 (see key b in Figure 8)in a chamber at Tmaxfor the specified holding time,th1.
b)During the last 15 min of holding time,operating mode is switched to 3.2 or 4.2 as defined in ISO 16750-1 (see key cin Figure 8)to induce self-heating of the DUT.
c)The operating mode is switched to 1.1 or 1.2 (see key a in Figure 8)and the DUT is moved into splash area within tt
d)The operating mode is switched to 3.2 or 4.2 again when the DUT has been set in test equipment for splash test.
e)Splash the DUT with cold water for 3 s (see key tsin Figure 8)within“tp-t1 ≤1min”.
f)After splash,the operating mode is continuously kept as 3.2 or 4.2 for 2 min or more (see key th2 in Figure 8).
g)The operating mode is switched to 1.1 or 1.2,and the DUT is moved back into a chamber.
If the DUT is splashed in the vehicle from only one direction,splash it from this direction only while it is in an as-installed position. If the DUT is splashed from various directions in the vehicle,then these directions shall betaken into account.In this case,use an additional DUT for each splash direction.The width of the splash directed at the DUT shall always be greater than the width of the DUT. If a DUT of considerable size is splashed and proven too big for one jet,arrange several jets in a row to produce a line of splash impact on the DUT,seeFigures 7 to 9.
Note 1: Difference between a high-pressure load during holding time and a low-pressure load during splash time can be caused by the initial humidity inside the DUT It is important to store the DUT for a sufficient time in the initial state defined as the general test condition (see ISO 16750-1).
Test parameters include the following. Number of cycles:100. Holding time,th1,at Tmax:lh or until thermal equilibrium of the DUT is obtained.The longest of the two durations shall be selected. First transfer time,tu1 :<20 s(for manual transfer of the DUT between temperature storage and splashing). The transfer time can be extended to 3 min by agreement between the customer and the supplier due to the size of the DUT or test setup feasibility. Second transfer time,t2:tt2 can be set in consideration of the effect of once again reaching temperature equilibrium in th1, Preparation time for splash,tp:tp-tt; ≤1 min.The preparation time for splash shall be as short as possible to minimise the temperature drop of the DUT. Test fluid: water. Water temperature:0°C to+4°C. Water flow: between 3l and 4I per 3s(splash time,ts). Holding time after splash,th2 :ample time to allow cold water to affect sealings, crevices,etc.on the DUT, but at least th2 >2 min. Distance between jet and DUT surface:(325±25)mm (water shall be applied over the complete width of the DUT) Test cycle: see Figure 8. Orientation of the DUT:as in the vehicle.
Note 2: As a background of possible extension to 3 min of the transfer time,in case of large DUT (e.g. commercial vehicle e-motor)the transfer time can be longer than 20 s for applying this test.
Note 3: The holding time at next cycle can be minimised by shortening ofthe second transfer time ofttz
Note 4: Substances such as colours, dust,salt or soap can be added to the water in order to improve detect ability. When using soap,a small amount of soap is sufficient for reduction of surface tension.If additional substances are added,these can cause corrosive effects in subsequent tests.
Figure 7 Jet
Figure 8 Test cycle for splash water test
Figure 9 Test set up for splash water test
The functional status shall be class A as defined in ISO 16750-1 during active operating modes	5.4.2.2 Requirement
Connect the DUT to the test equipment.Operate the DUT in a chamber at Tmax as defined in Table 1 for the specified holding time, th. With the device still operating,submerge it for 5 min in a cold-water tank, in a depth equal to or greater than 10 mm (see Figure 10).Although operation of the DUT should be kept during the submersion,it is allowed to change its operating modes from 3.2 or 4.2 to 1.2 only during the submersion if agreed between the customer and the supplier due to safety in test.	5.4.3.1 Test method	5.4.3 Submersion test
Test parameters include: Number of cycles:10. Holding time t,at Tmax:1 h or until thermal equilibrium of DUT is obtained.The longest of the two durations shall be selected. Transfer time,t:<20s. The transfer time can be extended to 3 min by agreement between the customer and the supplier due to the size of DUT or test setup feasibility. Test fluid: water. Water temperature :0°C to +4°C. Immersion time:5 min. Operating mode:3.2 or 4.2 as defined in ISO 16750-1. Orientation of the DUT: as in the vehicle.
Note 1: As a background of possible extension to 3 min of the transfer time,in case of large DUT (e.g. commercial vehicle e-motor)the transfer time can be longer than 20s for applying this test.
Note 2: Substances such as colours, dust,salt or soap can be added to the water in order to improve detect ability. When using soap,a small amount of soap is sufficient for reduction of surface tension.Before adding additional substances,itis noted that these can cause corrosive effects in subsequent tests.
Figure 10 DUT in a cold-water tank
The functional status shall be class A as defined in ISO 16750-1 during active operating modes.	5.4.3.2 Requirement

ISO16750-4 Road Vehicles- Environmental Conditions and Testing for Electrical and Electronic Equipment – Part 4: Climatic Loads｜5.4 Cold Water Shock Tests	Test Standard:
VOLKSWAGEN VW80000 Electric and Electronic Components in Motor Vehicles up to 3.5 t General Requirements, Test Conditions, and Tests｜11.12 K-12 Thermal Shock with Splash Water｜11.13 K-13 Thermal Shock Immersion
Mercedes-Benz MBN LV 124-2 Electric and Electronic Components in Motor Vehicles up to 3,5t – General Requirements, Test Conditions and Tests｜Part 2: Environmental Requirements → 14.12 K-12 Thermal Shock With Splash Water｜14.13 K-13 Thermal Shock Immersion

Where these tests apply on a vehicle ? Cold water shock tests are directly connected to the real-world operating conditions of modern vehicles. Automotive engineers must consider where sudden thermal shocks can realistically occur and which components are most vulnerable when exposed to cold water quenching after being heated during operation. Concerning the test samples, they are never the same, but we can have battery, compressor, motor, and other pieces from the automotive field. In practice, test objects range from 12V and 48V batteries, air conditioning compressors, electric traction motors, and control modules, to smaller relay boxes and actuators.

Each sample has its own geometry, thermal mass, and sealing requirements, which is why cold water shock testing must be tailored to the unique properties of the device under test. The wide scope of potential applications highlights the importance of customizing cold water shock test procedures. Components in the engine bay may require high-temperature preconditioning, while battery enclosures or electric drive units demand deeper immersion cycles to reflect actual risk scenarios. By clearly mapping test methods to the component location and function, engineers not only comply with ISO 16750-4, VW 80000, and MBN LV 124-2 requirements but also build stronger confidence in long-term vehicle durability.

Pumps, valves, and ECUs located near radiators, turbochargers, or exhaust systems are exposed to extreme heat cycles. When these parts suddenly encounter cold water from puddles, rain splash, or pressure washing, the risk of cracking housings or seal damage increases significantly. Verifying durability under cold water shock conditions ensures reliability in demanding under-hood environments.	Engine Bay & Powertrain Peripherals:
Sensors, wiring harness junctions, and lighting modules are typically positioned close to the road surface. These elements frequently come into contact with water splash, mud, and road contaminants. Cold water shock tests help confirm that delicate underbody electronics and connectors can resist sudden temperature drops and repeated splash cycles without malfunction or water ingress.	Chassis & Underbody:
PTC heaters, cooling fans, and battery auxiliaries in hybrid and electric vehicles operate at elevated temperatures. When these components are suddenly cooled with near-freezing water, the thermal stress can cause deformation or seal failure. By simulating splash water test and submersion test conditions, manufacturers verify the integrity of critical thermal management devices that support safe vehicle operation.	Thermal Management Systems:
Boots, grommets, and connector seals that are positioned in splash paths represent weak points in many vehicle assemblies. A connector that leaks during a cold water shock test may lead to short circuits, sensor errors, or complete system shutdown. These components are therefore prime candidates for both splash water tests and immersion evaluations in line with ISO 16750-4 and OEM standards.	Connectors & Sealing Interfaces: