ISO 16750-4:2023

INTERNATIONAL ISO
STANDARD 16750-4
Fourth edition
2023-07
Road vehicles — Environmental
conditions and testing for electrical
and electronic equipment —
Part 4:
Climatic loads
Véhicules routiers — Spécifications d'environnement et essais de
l'équipement électrique et électronique —
Partie 4: Contraintes climatiques
Reference number
ISO 16750-4:2023(E)
© ISO 2023

---------------------- Page: 1 ----------------------
ISO 16750-4:2023(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
  © ISO 2023 – All rights reserved

---------------------- Page: 2 ----------------------
ISO 16750-4:2023(E)
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Operating temperature ranges . 2
5 Tests and requirements .4
5.1 Tests at constant temperature . 4
5.1.1 Low-temperature tests . 4
5.1.2 High-temperature tests . 4
5.2 Temperature step test . 5
5.2.1 Purpose . 5
5.2.2 Test method . 5
5.2.3 Requirement . 6
5.3 Temperature cycling tests . 6
5.3.1 Temperature cycle with specified change rate . 6
5.3.2 Rapid change of temperature with specified transition duration .13
5.4 Cold water shock tests . 15
5.4.1 Purpose .15
5.4.2 Splash water test . 15
5.4.3 Submersion test . 19
5.5 Salt spray tests . 20
5.5.1 General .20
5.5.2 Corrosion test . 21
5.5.3 Leakage and function test . 21
5.5.4 Salt spray active test for rotating machines with open housing .22
5.5.5 Salt spray combined cycle test . 24
5.5.6 Cyclic corrosion test . 26
5.6 Humid heat, cyclic tests . 27
5.6.1 Purpose . 27
5.6.2 Test method . 27
5.6.3 Requirements .30
5.7 Damp heat, steady state test . 30
5.7.1 Purpose .30
5.7.2 Test method . 30
5.7.3 Requirements .30
5.8 Condensation test. 31
5.8.1 Purpose . 31
5.8.2 Test method . 31
5.8.3 Requirement . 35
5.9 Corrosion test with flow of mixed gas . 35
5.9.1 Purpose . 35
5.9.2 Test method . 35
5.9.3 Requirement . 35
5.10 Solar radiation test . 35
5.10.1 Purpose . 35
5.10.2 Test method . 35
5.10.3 Requirements .36
5.11 Dust test . . . 36
5.11.1 Purpose . 36
5.11.2 Test method . 36
5.11.3 Requirements .38
5.12 Atmospheric pressure test . .38
5.12.1 Purpose .38
iii
© ISO 2023 – All rights reserved

---------------------- Page: 3 ----------------------
ISO 16750-4:2023(E)
5.12.2 Test method .38
5.12.3 Requirements .39
6 Code for climatic loads . .39
7 Protection against water and foreign objects .41
8 Documentation .41
Annex A (informative) Usual tests and requirements for equipment depending on the
mounting location.42
Annex B (informative) Background information to determine the number of cycles of the
salt spray combined cycle test .47
Annex C (informative) Insulation tests .52
Annex D (informative) The necessity of testing atmospheric pressure .55
Bibliography .59
iv
  © ISO 2023 – All rights reserved

---------------------- Page: 4 ----------------------
ISO 16750-4:2023(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use
of (a) patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed
patent rights in respect thereof. As of the date of publication of this document, ISO had not received
notice of (a) patent(s) which may be required to implement this document. However, implementers are
cautioned that this may not represent the latest information, which may be obtained from the patent
database available at www.iso.org/patents. ISO shall not be held responsible for identifying any or all
such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 32,
Electrical and electronic components and general system aspects.
This fourth edition cancels and replaces the third edition (ISO 16750-4:2010), which has been
technically revised.
The main changes are as follows:
— integration and harmonization of contents from ISO 19453-4:2018 (e.g. addition of 5.8 and 5.12);
— subdivision of test methods in temperature cycle test for application to DUTs of "small and
lightweight" or "large and heavy" size (5.3);
— addition of test methods for large and heavy DUTs in cold water shock test (5.4);
— addition of three salt spray corrosion tests (5.5.4, 5.5.5 and 5.5.6);
— addition of concrete test method and requirements in solar radiation test (5.10);
— addition of optional test method in dust test for DUT installed in passenger compartment or luggage/
load compartment (5.11);
— addition of new tests and the selection of applied cycles in rapid change of temperature with
specified transition duration (Clause 6, Table 10);
— subdivision of mounting location defining the corresponding severities (Annex A);
— error correction (Annex B, Figure B.1, B.2 and Table B.1 taken over from ISO 19453-4:2018);
v
© ISO 2023 – All rights reserved

---------------------- Page: 5 ----------------------
ISO 16750-4:2023(E)
— clarification of technical background to determine number of cycles and severities according to the
mounting location (Annex B, Clause B.4);
— subdivision of electric isolation test methods for voltage class A and voltage class B (Annex C).
A list of all parts in the ISO 16750 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
vi
  © ISO 2023 – All rights reserved

---------------------- Page: 6 ----------------------
INTERNATIONAL STANDARD ISO 16750-4:2023(E)
Road vehicles — Environmental conditions and testing for
electrical and electronic equipment —
Part 4:
Climatic loads
1 Scope
This document applies to electric and electronic systems and components for vehicles including electric
propulsion systems and components with maximum working voltages according to voltage class B. It
describes the potential environmental stresses and specifies tests and requirements recommended for
the specific mounting location on/in the vehicle.
This document describes climatic loads.
This document is not intended to apply to environmental requirements or testing for systems and
components of motorcycles and mopeds.
Systems and their components released for production, or systems and their components already under
development prior to the publication date of this document, can be exempted from fulfilling the changes
in this edition compared to the previous one.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 4892-2, Plastics — Methods of exposure to laboratory light sources — Part 2: Xenon-arc lamps
ISO 4892-3, Plastics — Methods of exposure to laboratory light sources — Part 3: Fluorescent UV lamps
ISO 4892-4, Plastics — Methods of exposure to laboratory light sources — Part 4: Open-flame carbon-arc
lamps
ISO 9227:2022, Corrosion tests in artificial atmospheres — Salt spray tests
ISO 11997-3, Paints and varnishes — Determination of resistance to cyclic corrosion conditions — Part 3:
Testing of coating systems on materials and components in automotive construction
ISO 16750-1, Road vehicles — Environmental conditions and testing for electrical and electronic
equipment — Part 1: General
ISO 16750-2, Road vehicles — Environmental conditions and testing for electrical and electronic
equipment — Part 2: Electrical loads
ISO 20653, Road vehicles — Degrees of protection (IP code) — Protection of electrical equipment against
foreign objects, water and access
ISO 21498-1, Electrically propelled road vehicles — Electrical specifications and tests for voltage class B
systems and components — Part 1: Voltage sub-classes and characteristics
ISO 21780, Road vehicles — Supply voltage of 48 V — Electrical requirements and tests
IEC 60068-1:2013, Environmental testing — Part 1: General and guidance
1
© ISO 2023 – All rights reserved

---------------------- Page: 7 ----------------------
ISO 16750-4:2023(E)
IEC 60068-2-1:2007, Environmental testing — Part 2-1: Tests — Test A: Cold
IEC 60068-2-2:2007, Environmental testing — Part 2-2: Tests — Test B: Dry heat
IEC 60068-2-11:2021, Basic environmental testing procedures — Part 2-11: Tests — Test Ka: Salt mist
IEC 60068-2-14, Environmental testing — Part 2-14: Tests — Test N: Change of temperature
IEC 60068-2-30:2005, Environmental testing — Part 2-30: Tests — Test Db: Damp heat, cyclic (12 h + 12 h
cycle)
IEC 60068-2-38, Environmental testing — Part 2-38: Tests — Test Z/AD: Composite temperature/humidity
cyclic test
IEC 60068-2-52:2017, Environmental testing — Part 2-52: Tests — Test Kb: Salt mist, cyclic (sodium
chloride solution)
IEC 60068-2-60:2015, Environmental testing — Part 2-60: Tests — Test Ke: Flowing mixed gas corrosion
test
IEC 60068-2-78, Environmental testing — Part 2-78: Tests — Test Cab: Damp heat, steady state
IEC 60664-1:2020, Insulation coordination for equipment within low-voltage systems — Part 1: Principles,
requirements and tests
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 16750-1 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Operating temperature ranges
Choose the applicable temperature range from Table 1 to be presented in the specifications of the DUT.
In the case of hot soak, choose from Table 2 the relative temperature increase ΔT and add it to the
HS
maximum temperature T to have the absolute hot-soak temperature (T ).
max maxHS
TT+=Δ T
maxHSmaxHS
For further details, refer to 5.3.1.
The paint repair temperature (T ) as defined in ISO 16750-1 can be set to a higher value than the
maxPR
operating temperature. Specify this temperature in the specifications of the DUT.
Table 1 — Operating temperature ranges
Code Minimum operating temperature Maximum operating temperature
T T
min max
[°C] [°C]
A −20 65
B −30 65
2
  © ISO 2023 – All rights reserved

---------------------- Page: 8 ----------------------
ISO 16750-4:2023(E)
TTabablele 1 1 ((ccoonnttiinnueuedd))
Code Minimum operating temperature Maximum operating temperature
T T
min max
[°C] [°C]
C 65
D 70
E 75
F 80
G 85
H 90
I 95
J 100
K 105
L 110
M 115
−40
N 120
O 125
P 130
Q 140
R 150
S 155
T 160
U 165
V 170
W 175
X 180
Z As agreed
Table 2 — Relative temperature increase in hot soak
Code ΔT
HS
[°C]
a 15
b 30
c 50
z As agreed
NOTE For DUTs with hot soak, the code letter is defined as a combination of Tables 1 and 2, e.g. Hb
(T = 90 °C and ΔT = 30 °C).
max HS
3
© ISO 2023 – All rights reserved

---------------------- Page: 9 ----------------------
ISO 16750-4:2023(E)
5 Tests and requirements
5.1 Tests at constant temperature
5.1.1 Low-temperature tests
5.1.1.1 Storage test
5.1.1.1.1 Purpose
This test simulates the exposure of the systems/components to low temperatures without electrical
operation, e.g. during shipment of the systems/components. The failure mode is a malfunction due to
insufficient frost resistance, e.g. the freezing of a coolant.
5.1.1.1.2 Test method
Perform the test in accordance with IEC 60068-2-1:2007, 5.2, Test Ab, at a temperature of −40 °C for
a duration of 24 h unless otherwise indicated in the DUT specification. The operating mode is 1.1 as
defined in ISO 16750-1.
5.1.1.1.3 Requirement
The functional status shall be class C as defined in ISO 16750-1.
5.1.1.2 Operation test
5.1.1.2.1 Purpose
This test simulates the exposure of the systems/components to low temperatures with electrical
operation, e.g. the use of the systems/components at very low ambient temperature. The failure mode
is an electrical malfunction caused by low temperature, e.g. the freezing of capacitors with liquid
electrolyte.
5.1.1.2.2 Test method
Perform the test in accordance with IEC 60068-2-1:2007, 5.2, Test Ab or 5.3, Test Ad, at a temperature
of T for a duration of 24 h. Test Ab is applied for non-heat-dissipating DUTs and Test Ad is applied for
min
heat-dissipating DUTs. The operating mode is 3.3 or 4.3 as defined in ISO 16750-1.
5.1.1.2.3 Requirement
The functional status shall be class A as defined in ISO 16750-1.
5.1.2 High-temperature tests
5.1.2.1 Storage test
5.1.2.1.1 Purpose
This test simulates the exposure of the systems/components to high temperatures without electrical
operation, e.g. during the shipment of the systems/components. The failure mode is insufficient heat
resistance, e.g. warping of plastic housings.
4
  © ISO 2023 – All rights reserved

---------------------- Page: 10 ----------------------
ISO 16750-4:2023(E)
5.1.2.1.2 Test method
Perform the test in accordance with IEC 60068-2-2:2007, 5.2, Test Bb, at a temperature of 85 °C for
a duration of 48 h unless otherwise indicated in the DUT specification. The operating mode is 1.1 as
defined in ISO 16750-1.
5.1.2.1.3 Requirement
The functional status shall be class C as defined in ISO 16750-1.
5.1.2.2 Operation test
5.1.2.2.1 Purpose
This test simulates the exposure of the systems/components to high temperatures with electrical
operation, e.g. the use of the systems/components at very high ambient temperature. The failure mode
is an electrical malfunction caused by high temperature, e.g. thermal degradation of components.
5.1.2.2.2 Test method
Perform the test in accordance with IEC 60068-2-2:2007, 5.2 Test Bb or 5.3 Test Bd, at a temperature of
T for a duration of 96 h. Test Bb is applied for non-heat-dissipating DUTs and Test Bd is applied for
max
heat-dissipating DUTs. The operating mode is 3.4 or 4.4 as defined in ISO 16750-1.
5.1.2.2.3 Requirement
The functional status shall be class A as defined in ISO 16750-1.
5.2 Temperature step test
5.2.1 Purpose
This test checks the mechanical and electrical device for malfunctions (including failure to change
properly between different operating modes) which may occur within a small section of the operating
temperature range.
This test mainly applies to small and lightweight components, but can also be used for large and heavy
components if agreed between the customer and the supplier. See a mass classification example in
ISO 16750-1:2023, Annex C.
5.2.2 Test method
Install the DUT in a temperature chamber. According to Figure 1, decrease the temperature in steps
of 5 °C from 20 °C to T , then increase the temperature in steps of 5 °C from T to T and then
min min max
decrease the temperature in steps of 5 °C from T to 20 °C (see Figure 1). Wait at each step until
max
the DUT has obtained thermal equilibrium. Perform functional tests with operating mode 3.2 in
accordance with ISO 16750-1 at minimum supply voltage, U , and at maximum supply voltage, U ,
Smin Smax
in accordance with the specified ISO 16750-2 code letter, at each temperature step. In addition, for
each temperature step transitions of the DUT between different operating modes shall also be verified
(e.g. change between operating modes 3.2 and 2.1). Switch the DUT off (operating mode 2.1) during
transition to the next temperature. If the DUT has a nominal supply voltage other than 12/24 V, this
test shall be performed by the voltage range corresponding to functional status class A as defined
in ISO 16750-1 according to agreement between the customer and the supplier. In case of 48 V, the
test shall be performed at the upper and lower voltage of nominal voltage range in accordance with
ISO 21780. In case of voltage class B, the test shall be performed at the upper and lower voltage of
unlimited operating capability in accordance with ISO 21498-1. For DUTs with multiple voltage supply
5
© ISO 2023 – All rights reserved

---------------------- Page: 11 ----------------------
ISO 16750-4:2023(E)
levels, e.g. 12 V supply and voltage class B supply, the combination of test voltages for each temperature
step shall be agreed between the customer and the supplier.
Key
T temperature, in °C
t time, in min
T minimum operating temperature (see Table 1)
min
T maximum operating temperature (see Table 1)
max
Figure 1 — Temperature step test
5.2.3 Requirement
For each temperature step between T and T , the DUT shall have functional status class A as
min max
defined in ISO 16750-1 for active operating modes.
5.3 Temperature cycling tests
5.3.1 Temperature cycle with specified change rate
5.3.1.1 Purpose
This test simulates varying temperatures with electrical operation of the systems/components, e.g.
during the use of the system/component at changing ambient temperature. If a system/component
is exposed to hot-soak temperatures (e.g. engine-mounted systems/components), an additional short
temperature peak is added during the high temperature stage of the profile to ensure proper function
during short temperature peaks. The electrical operation is switched off during stages of decreasing
temperature to avoid electrical heat dissipation of the system/component which would inhibit reaching
T inside the system/component. The failure mode is an electrical malfunction during temperature
min
change.
The mass of the DUT is the main influence factor that determines the design of the temperature cycle.
This test shall be selected from 5.3.1.2 or 5.3.1.3 in accordance with mass classification example in
ISO 16750-1:2023, Annex C.
NOTE 1 This test is not intended to be a life test.
NOTE 2 For applying this test, it is important to calculate and check the temperature change rate against
available test chamber capabilities. If the specified chang
...