Technical Service Bulletin
87 Air conditioning refrigerant circuit diagnostic method using calibration gas
87 23 51 2064077/2 August 18, 2023. Supersedes Technical Service Bulletin Group 87 number 22-24 dated April
15, 2022, for reasons listed below.
Model(s)

© 2023 Audi of America, Inc.

Year

VIN Range

Vehicle-Specific Equipment

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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
Model(s)

Year

A4 allroad, A4, S4,
A5, A5 Cabriolet, A5
Sportback, S5, S5
Cabriolet, S5
Sportback, A6, S6
A7, S7, Q3, A5, SQ5,
and Q7,

2018 – 2024

TT, TTS, and TT
Roadster

2018 – 2023

A3 Cabriolet

2018 - 2019

A3, and S3

2018 – 2020
2022 – 2024

RS 3

2018 – 2020
2024

RS 5

Required

Required

All

Not Applicable

2018 – 2019
2021 - 2024

RS 7

2018
2021 - 2024

A8

2018 – 2021
2024
2018

S8

2020 – 2021
2023

R8, and R8 Spyder
TT RS
RS 5 Sportback

e-tron quattro

2018
2020 – 2023
2018 – 2022
2019
2021 – 2024
2019
2021 – 2023

Q8

2019 – 2024

A6 allroad, e-tron
Sportback quattro,
SQ7, SQ8, and RS
Q8

2020 – 2024

A8 e quattro

2020 – 2021

Condition
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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
REVISION HISTORY
Revision

Date

Purpose

2

-

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

1

04/15/2022

Initial publication

The cabin air conditioning cooling capacity is insufficient or without function on an R134a or R1234yf refrigerant
system equipped vehicle.

Technical Background
When a refrigerant circuit leak is determined as the root cause of a cabin cooling insufficiency it has traditionally
been diagnosed using either the addition of a contrast dye into the circuit and inspection using ultraviolet light, the
use of an electronic halogen leak detector, or filling the circuit with pressurized nitrogen and searching for the leak
by applying a liquid soap and water solution and inspecting the circuit for the presence of bubble formation. These
methods can be unreliable, particularly when diagnosing a possible refrigerant leak in the evaporator core.
When diagnosing a possible leak from an evaporator core, false-positive readings from a halogen leak detector
are common and visual access to the evaporator core in an attempt to inspect for the presence of contrast dye or
bubble formation is problematic at the very least.
An additional diagnostic method is now available to analyze a refrigerant leak in the circuit of an R134a or
R1234yf refrigerant system using calibration gas (95% nitrogen / 5% hydrogen) and an electronic hydrogen
detector (VAS523003A). Leak detection using calibration gas has been found to be more effective when
diagnosing a leak source in the areas of the refrigerant circuit that are extremely difficult to access (e.g. the
evaporator core concealed inside the evaporator housing).

Production Solution
Beginning with the R744 refrigerant system in the new Q4 e-tron the leak detection method for this refrigerant
system requires a process that prohibits the use of additives of any kind when diagnosing a leak, creating the
need for a leak detection method using calibration gas. This requires a new tool set. The AT-448 Tool Set Audi
R744 CO2 A/C Service Introduction (See Service Information circular – Special Tools and Equipment number
ATE-21-21) is now released to all dealers. The tools in this set can be adapted to diagnose R134a and R1234yf
refrigerant circuit leaks as well.

Service

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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
Note:
The procedure in this TSB describes a method for leak detection for R134A and R1234yf refrigerant platforms
only. While the diagnostic method for the R744 system in the Q4 e-tron is similar there are important differences
in the procedure and, as such, should be carried out using the procedure in ElsaPro.
Warning:
Extreme caution must be exercised when handling and using calibration gas. The hydrogen component of the
gas mixture is flammable. Failure to employ proper handling and use protocol invites the risk of serious personal
injury or death.
1.

Should the vehicle arrive with insufficient cabin cooling from the air conditioning system recover the
refrigerant remaining in the circuit and compare this amount to the specified volume. A significantly lesser
amount recovered (>50% of total volume lost) indicates an active refrigerant circuit leak.

2.

Obtain a tank of calibration gas (95% nitrogen /
5% hydrogen) (Figure 1). This will need to be
sourced locally (e.g. Airgas®).

Figure 1. Calibration gas (95% Nitrogen / 5% Hydrogen).

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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
3.

The pressure regulator included in the
NITROKITG will not be used as it is only
suitable for connection to a gas tank containing
non-flammable gasses such as nitrogen (righthand thread). The AT-448 Tool Set includes the
VAS 584005 pressure regulator suitable for
connection to a gas tank containing any
flammable component as is the case with the
hydrogen component in calibration gas (lefthand thread). Connect the VAS 584005
pressure regulator to the tank (Figure 2). Make
sure the tank valve remains closed.

Figure 2. VAS 584005 pressure regulator attached to the
calibration gas tank.
4.

Set the HVAC settings to full defrost. Close all of the instrument panel vents and make sure that the fresh
air intake is also closed (recirculation mode). Close off the cabin completely (windows, sunroof, doors, rear
lid, etc.). Then turn off the vehicle completely (key off, no blower activation).

5.

When servicing a high voltage vehicle de-energize the vehicle.

6.

The NITROKITG includes a service hose and high side service port snap coupler for both an R134a and
R1234yf refrigerant system. This will allow the single connection to the refrigerant circuit of both an R134a
as well as an R1234yf equipped vehicle. Use the snap coupler appropriate for the refrigerant platform being
serviced from the NITROKITG to complete the connection.

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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
7.

Evacuate the vehicle refrigerant circuit for 15
minutes. After the refrigerant circuit is free of
any refrigerant connect the service manifold
from the NITROKITG Automotive A/C Nitrogen
Leak Test Kit to the high side service port. Use
the appropriate snap coupler for the platform of
the circuit being serviced. (Figure 3).

Figure 3. NITROKITG manifold connected to the high
side service port.
8.

Only one of the ports needs to be connected for
this diagnosis. The connection to the high side
port is shown in Figure 4.

Figure 4. NITROKITG high side snap coupler connected
to the high side service port.

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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
9.

Connect the VAS 584005 Pressure Reducer to
the NITROKITG manifold. Fill the circuit with
calibration gas to an absolute pressure of no
greater than 14 bar (Figure 5).

Figure 5. Calibration gas pressure in the circuit.
Note:
The air conditioning system must not be activated while the circuit is charged with calibration gas. Running the
air conditioning system while it is charged with calibration gas will damage the compressor.
If necessary apply a warning sign to the vehicle stating “Do Not Run” or a similar warning to prevent accidental
operation while the circuit is filled with calibration gas for the purposes of diagnosis.
10. After the circuit is charged allow the circuit pressure to equalize for 20 minutes. Leak detection can then
begin.

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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
11. Close off the defroster outlets with masking
tape leaving a small opening for the VAS
523003A gas leak detector probe (Figure 6).

Figure 6. VAS 523003A gas leak detector in place in the
defroster outlet.
12. The gas leak detector VAS 523003A reacts to
the hydrogen component in the calibration gas.
Since hydrogen is lighter than air, it will rise to
the position of the detector probe. The
hydrogen content in the calibration gas,
however, evaporates after a short period of time
(Figure 7).
Perform the leak diagnosis immediately after
charging the refrigerant circuit with calibration
gas and the 20-minute equalization period.
Depending on the conditions, it may be
necessary to recharge the refrigerant circuit
with calibration gas in an attempt to clearly
identify a circuit leak at the evaporator core.

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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
Figure 7. VAS 523003A in place in the defroster outlet
and hydrogen presence is detected.
13. If no leak is detected through the defroster outlet using this method the evaporator core is not the source of
the refrigerant leak and the evaporator core is not to be replaced. Continue diagnosis using the VAS
523003A along all remaining components of the refrigerant circuit to determine the source of the leak.
14. When any and all leak sources have been identified close the valve on the top of the calibration gas
tank. Any calibration gas that remains in the refrigerant circuit can be slowly ventilated until the circuit
pressure has equalized with atmospheric pressure. Proceed with the necessary repairs, evacuate the
refrigerant circuit, and recharge the system as necessary.
15.

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 8,
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 8. Relay and fuse carrier 3 –SR3-

16. When re-energizing a high voltage vehicle observe the following:

Warranty
Claim Type:

• 110 Up to 48 Months/50,000 Miles.
• G10 for CPO Covered Vehicles – Verify Owner.
• If the vehicle is outside of any warranty, this Technical Service Bulletin is
informational only.

Service Number:
© 2023 Audi of America, Inc.

8760

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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
Damage Code:

0050

Labor Operations:

Evaporator remove and reinstall

8760 1950

See SRT with
associated
operations

8515 1950

See SRT with
associated
operations

Air conditioner check

8760 0199

Time necessary
for diagnosis
supported by
punch time (Max
130 TU)

GFF

No allowance

0 TU

Road test prior to the service procedure

No allowance

0 TU

Road test after the service procedure

No allowance

0 TU

(All models except e-tron GT)
Heating, ventilation unit remove and reinstall
(e-tron GT)

Diagnostic Time:

Claim Comment:

As per TSB 2064077/2

All warranty claims submitted for payment must be in accordance with the Audi Warranty Policies and Procedures
Manual. Claims are subject to review or audit by Audi Warranty.

Required Parts and Tools
Tool Number

Tool Description

VAS581009

R744 CO2 A/C Service Unit

© 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
VAS584005

Pressure Reducer and Hose
NITROKITG

Automotive A/C Nitrogen Leak Test Kit
VAS523003A

Gas Leak Detector

Additional Information
All part and service references provided in this TSB (2064077) 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.

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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
©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
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.