Technical Service Bulletin
87 Air conditioning does not cool; B10AE21
87 23 52 2063575/3 August 18, 2023. Supersedes Technical Service Bulletin Group 87 number 22-28 dated July
12, 2022, for reasons listed below.
Model(s)

Year

VIN Range

Vehicle-Specific Equipment

All

Not Applicable

Q5, Q5 e quattro,
2020 – 2024
and SQ5
Q5 Sportback,
and SQ5
Sportback

2021 – 2024

A4, A4 allroad,
S4, A5, A5
Cabriolet, A5
Sportback, S5,
2022 – 2024
S5 Cabriolet, S5
Sportback, RS 5,
RS 5 Sportback,
Q7, and SQ7

Condition
REVISION HISTORY
Revision

Date

Purpose

3

-

Revised header (Add Model Year 2024)
Revised Service (Add relay and fuse carrier suggestion)

2

07/12/2022

Revised header (Add Model Years, Models)
Revised Technical Background (More specific description of condition)
Revised Service (Additional diagnostic steps and method, revised
documentation requirement, revised part submission requirement)

1

06/16/2021

Initial publication

Customer states:
• The air conditioning does not blow cold enough, takes a long period of time to cool, or does not cool at all.

Technical Background

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intellectual property rights of Audi of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this
document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites, without the prior expressed written permission of the publisher.

Technical Service Bulletin
The refrigerant circuit head pressures are checked,
found to be insufficient and after recovering the
refrigerant volume the diagnostic finding is
determined that the refrigerant volume in the circuit is
very low or empty. DTC B10AE21 (High-pressure
sensor Lower limit not reached) may be stored in the
Heating/Air Conditioning Electronics control module,
E87 (address word 0008). Leak identification dye is
added to the refrigerant circuit along with a full charge
of the refrigerant and the vehicle is test
Figure 1. HVAC evaporator and housing.
driven. Correct cabin cooling is restored. A visual
inspection of the refrigerant circuit is conducted and
no obvious leak can be seen under UV lighting. When
using an electronic refrigerant leak detector at the
central vents and condensate drain it alerts that the
evaporator core may be the source of the leak.

Production Solution
Several improvements have been implemented in the evaporator core resulting in a more robust unit resistant to
leaking refrigerant.

Service
The vast majority of the evaporator cores replaced in the models for which this TSB appears have been
returned, laboratory tested, and found to not have any leak whatsoever. This evidence confirms that while
replacement of the evaporator core appears to solve the refrigerant leak, the root cause of the leak is not the
evaporator core itself but likely a compromised connection at any of the expansion valve connections to/from the
evaporator or at any other refrigerant connection, hose or component in the refrigerant circuit. If the refrigerant
leak is in the cowl or engine compartment area for example, the free refrigerant migrates through the fresh air
intake and into the evaporator housing. This generates a false positive evaporator core leak reading from the
cabin air outlet vents when using a halogen leak detector. The evaporator core is incorrectly diagnosed as the
sole source of the leak in these cases.
Note:
It has been determined that a halogen leak detector is not the most reliable method for precisely locating a
refrigerant leak, particularly in an evaporator core where direct access to the core is not possible. It is strongly
recommended that the use of calibration gas using the tools and procedure outlined in TSB 2064077 87 Air
conditioning refrigerant circuit diagnostic method using calibration gas be used as the diagnostic method where
a suspected evaporator leak is concerned.

© 2023 Audi of America, Inc.

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All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other
intellectual property rights of Audi of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this
document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites, without the prior expressed written permission of the publisher.

Technical Service Bulletin
If, after checking for
refrigerant leaks at
each component
and connection in
the refrigerant
circuit and
systematically
excluded as a
cause, your
diagnostic
conclusion is that
the evaporator core
is the only
refrigerant leak in
Figure 2. Refrigerant connections in need of closer
the entire circuit
observation.
apply a high level of
scrutiny to the
connection junction
at the evaporator
core /expansion
valve/refrigerant
lines for a possibly
overlooked leak in
these areas (figures
2 - 3).

Figure 3. Refrigerant connections to the expansion
valve.

© 2023 Audi of America, Inc.

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All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other
intellectual property rights of Audi of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this
document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites, without the prior expressed written permission of the publisher.

Technical Service Bulletin
If a refrigerant leak
is detected from the
evaporator
core/expansion and
valve/refrigerant line
junction, take a
short video showing
the diagnostic
confirmation of a
leak in this area and
post it to DocIT. Then, replace
the expansion valve
and all four O-rings Figure 4. Leak at expansion valve connection
evidenced by residue from the contrast agent.
without replacing
the evaporator
(figure 4). Re-test to
ensure that the
refrigerant leak is
solved without the
replacement of the
evaporator
core. Photograph
any damage to the
expansion valve
ports, damaged orings, or refrigerant
line connections
and post these to
Doc-IT as well.
Should your diagnostic process conclude, however, that any and all leak
possibilities from the expansion valve connections (between the evaporator
and expansion valve, between the expansion valve and high and low
refrigerant lines) or at any other refrigerant connection, hose or component
in the refrigerant circuit have been excluded as a cause and replacement of
the evaporator core is the only logical course of action that remains then
replace the evaporator housing with evaporator core assembly along
with the expansion valve, retaining plate and bolts (included in small
parts kit 4M0 898 037 A) and all four o-ring seals.
Do not replace only the evaporator housing with core assembly. Do not
loosen or remove the expansion valve from the evaporator core
connections in any way. Do not disassemble the evaporator housing
assembly in any way. Ensure that the evaporator housing assembly,
retaining plate and bolts and expansion valve are carefully packaged

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All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other
intellectual property rights of Audi of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this
document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites, without the prior expressed written permission of the publisher.

Technical Service Bulletin
securely as a single unit. This entire assembly will be requested for
submission and laboratory analysis.
Note:
Should the evaporator for the Q5 be confirmed
leaking by way of this diagnostic procedure and
replacement of the evaporator is performed it is
necessary to loosen and refasten the Relay and
Fuse Carrier 3 -SR3- (shown in figure 5,
position 1) in the course of the repair. During
reassembly of the vehicle it is critically
important that this relay and fuse carrier in
particular be reinstalled in its correct original
position. Failure to reinstall the Relay and Fuse
Carrier 3 precisely will result in water intrusion
and subsequent component damage.
Figure 5. Relay and fuse carrier 3 –SR3Note:
The complete evaporator housing assembly, expansion valve, bolts and o-ring seals as described in this TSB
received in the WPRC incomplete, disassembled or determined to include components confirmed to not be the
original components from the case (verified through component serial numbers and production dates) as
specified in this TSB will be returned to the dealer and the claim debited.

Warranty
This TSB is informational only and not applicable to any Audi Warranty.

Required Parts and Tools
Tool Number

© 2023 Audi of America, Inc.

Tool Description

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All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other
intellectual property rights of Audi of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this
document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites, without the prior expressed written permission of the publisher.

Technical Service Bulletin
Various

Electronic Refrigerant Leak Detector
NITROKITG

Automotive A/C Nitrogen Leak Test Kit
VAS 6160/VAS 6150

VAS tester with the current version of ODIS (Windows 10)

Additional Information
The following Technical Service Bulletin will be necessary to complete this procedure:
• TSB 2064077 87 Air conditioning refrigerant circuit diagnostic method using calibration gas
All part and service references provided in this TSB (2063575) are subject to change and/or removal. Always
check with your Parts Department and/or ETKA for the latest information and parts bulletins. Please check the
Repair Manual for fasteners, bolts, nuts, and screws that require replacement during the repair.
©2023 Audi of America, Inc. All rights reserved. The information contained in this document is based on the
latest information available at the time of printing and is subject to the copyright and other intellectual property
rights of Audi of America, Inc., its affiliated companies, and its licensors. All rights are reserved to make changes
at any time without notice. No part of this document may be reproduced, stored in a retrieval system, or
transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may

© 2023 Audi of America, Inc.

Page 6 of 7

All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other
intellectual property rights of Audi of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this
document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites, without the prior expressed written permission of the publisher.

Technical Service Bulletin
these materials be modified or reposted to other sites without the prior expressed written permission of the
publisher.

© 2023 Audi of America, Inc.

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All rights reserved. Information contained in this document is based on the latest information available at the time of printing and is subject to the copyright and other
intellectual property rights of Audi of America, Inc., its affiliated companies and its licensors. All rights are reserved to make changes at any time without notice. No part of this
document may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, nor may
these materials be modified or reposted to other sites, without the prior expressed written permission of the publisher.