Audi Audi S5 2017-present HVAC System Bolt Torque Specifications
Audi Audi S5 2017-present

Audi Audi S5 2017-present HVAC System Bolt Torque Specifications

Detailed torque specifications for bolts related to the HVAC system of the 2017-Present Audi S5 (B9) generation. Includes compressor, condenser, and evaporator component mounting bolts.

Updated

Important Information

Safety guidelines and reference information for proper torque application

Quick Reference Guide
ft-lbs → Nm
× 1.356
ft-lbs → kg-m
× 0.138
Nm → ft-lbs
× 0.738
in-lbs → ft-lbs
× 0.083

Common Torque Patterns

Star Pattern

Used for wheels and other circular bolt patterns

Star Pattern torque pattern diagram showing proper bolt tightening sequence
Cross Pattern

Used for gaskets and cover plates

Cross Pattern torque pattern diagram showing proper bolt tightening sequence
Sequential Pattern

Used for head bolts and other critical components

Sequential Pattern torque pattern diagram showing proper bolt tightening sequence

Common Mistakes to Avoid

Over-tightening

Exceeding the specified torque value can stretch or break fasteners, damage threads, or crack components.

Prevention:

Always use a calibrated torque wrench and follow specifications exactly.

Incorrect Torque Sequence

Tightening bolts in the wrong order can cause uneven pressure distribution and potential leaks or damage.

Prevention:

Follow the manufacturer's specified torque sequence pattern.

Dirty Threads

Dirt, rust, or old thread locker can affect torque readings and proper fastener tension.

Prevention:

Clean and inspect all threads before assembly. Use new thread locker if specified.

Reusing TTY Bolts

Torque-to-yield bolts are designed to stretch and must not be reused.

Prevention:

Always replace TTY bolts with new ones. They are single-use only.

Dry vs. Lubricated

Not accounting for whether torque specs are for dry or lubricated fasteners can lead to incorrect tension.

Prevention:

Check if specs are for dry or lubricated threads. Use specified lubricant when required.

Recommended Tools

Torque Wrench (1/4" Drive)

Range: 2-25 ft-lbs
Small fasteners, delicate components

Torque Wrench (3/8" Drive)

Range: 10-100 ft-lbs
Most common automotive fasteners

Torque Wrench (1/2" Drive)

Range: 30-250 ft-lbs
Large fasteners, wheels

Angle Gauge

Torque-to-yield (TTY) bolts

Torque Wrench Care

  • Calibrate annually or after 5,000 clicks
  • Store at lowest setting
  • Keep clean and lubricated

Search Specifications

Search by component name, bolt size, or description

Torque Calculator

Convert between different torque units

Ac Compressor

Specifications for mounting and component bolts related to the AC compressor, including the compressor itself, clutch and associated lines.

1

AC Compressor Mounting Bolts

M8 x 1.25 or M10 x 1.5
Torque Value
18 ft-lbs (25 N·m)
Important Notes
Bolts secure the AC compressor to the engine block or mounting bracket. Proper torque ensures firm mounting, preventing vibration and misalignment. Estimated bolt size based on similar applications.
2

AC Compressor Clutch Bolt

M6 x 1.0 or M8 x 1.25
Torque Value
15 ft-lbs (20 N·m)
Important Notes
Central bolt securing the compressor clutch to the compressor shaft. Correct torque prevents slippage and damage. Estimated based on industry standards for clutch bolts.
3

AC Compressor Line Connections

Specific to fitting
Torque Value
12 ft-lbs (16 N·m)
Important Notes
Secures refrigerant lines to the compressor. Typically uses flared fittings with compression seals. Correct torque is crucial to prevent refrigerant leaks. Estimated, based on industry standard for flared fittings.

Condenser

Specifications for mounting and line connection bolts related to the AC condenser.

1

Condenser Mounting Bolts/Screws

M6 x 1.0
Torque Value
7 ft-lbs (10 N·m)
Important Notes
Secures the condenser to the front of the vehicle. Proper torque prevents vibration. Estimated bolt size based on typical condenser mountings.
2

Condenser Line Connections

Specific to fitting
Torque Value
12 ft-lbs (16 N·m)
Important Notes
Secures refrigerant lines to the condenser. Usually special fittings or banjo bolts with copper washers. Estimated, based on industry standard for flared fittings.

Evaporator

Specifications for mounting and component bolts related to the evaporator core and expansion valve.

1

Evaporator Core Mounting Screws/Bolts

Self-tapping or M4 x 0.7
Torque Value
5 ft-lbs (7 N·m)
Important Notes
Secures the evaporator core inside the HVAC housing. Typically small self-tapping screws. Estimated value based on plastic component fitment.
2

Expansion Valve Mounting Bolts/Screws

M6 x 1.0
Torque Value
7 ft-lbs (10 N·m)
Important Notes
Secures the expansion valve to the evaporator core or firewall. Often small M6 bolts or screws. Estimated value based on typical expansion valve mounting.

Hvac Housing

Specifications for bolts related to the HVAC housing, blower motor, actuators and sensors.

1

HVAC Blower Motor Mounting Screws

Self-tapping or M4 x 0.7
Torque Value
5 ft-lbs (7 N·m)
Important Notes
Secures the blower motor to the HVAC housing. Typically small self-tapping screws. Estimated based on similar HVAC units.
2

HVAC Housing Assembly Bolts (Larger Bolts)

M6 x 1.0 or M8 x 1.25
Torque Value
10 ft-lbs (14 N·m)
Important Notes
Secures the HVAC housing halves together or to the vehicle. Ensures the housing is properly sealed. Estimated based on similar HVAC housings.
3

HVAC Housing Assembly Screws (Smaller Screws)

Self-tapping or M4 x 0.7
Torque Value
5 ft-lbs (7 N·m)
Important Notes
Secures smaller HVAC components within the housing or housing covers and panels. Estimated based on similar HVAC units.
4

Temperature Sensor Mounting Screws

Self-tapping or M3 x 0.5
Torque Value
3 ft-lbs (4 N·m)
Important Notes
Secures delicate sensors to the HVAC housing or ductwork. Low torque required to prevent damage. Estimated value.
5

Actuator Mounting Screws

M4 x 0.7 or M5 x 0.8
Torque Value
4 ft-lbs (5 N·m)
Important Notes
Mounts actuators for various HVAC functions. Proper torque prevents gear bind issues. Estimated value based on similar actuators.

Receiver Drier

Specifications for mounting and line connections related to the receiver drier or accumulator.

1

Receiver Drier/Accumulator Mounting Bolts

M6 x 1.0 or M8 x 1.25
Torque Value
10 ft-lbs (14 N·m)
Important Notes
Secures the receiver drier/accumulator to the chassis or mounting bracket. Proper torque is necessary to prevent vibration. Estimated value based on similar components.
2

Receiver Drier/Accumulator Line Connections

Specific to fitting
Torque Value
12 ft-lbs (16 N·m)
Important Notes
Secures refrigerant lines to the receiver drier/accumulator. Ensures a leak-free seal. Estimated, based on industry standard for flared fittings.

Refrigerant Lines

Specifications for flared fittings used throughout the HVAC system

1

Refrigerant Line Connections (General)

Specific to fitting
Torque Value
12 ft-lbs (16 N·m)
Important Notes
General torque specification for all flared refrigerant line connections in the system. Estimated, based on industry standard for flared fittings.

Troubleshooting Guide

Common issues, diagnostic steps, and prevention guidelines

Common Issues

Bolt stretching, stripped threads, uneven torque patterns

Loose Components

Symptoms:
  • Rattling or vibration noises
  • Visible movement in components
  • Uneven panel gaps
Solutions:
  • Clean threads and mounting surfaces
  • Replace damaged fasteners
  • Apply proper torque in sequence
  • Use thread locker if specified

Stripped Fasteners

Symptoms:
  • Unable to achieve proper torque
  • Fastener spins freely
  • Visible thread damage
Solutions:
  • Use thread repair kit if appropriate
  • Install thread insert (HeliCoil)
  • Replace component if threaded hole is damaged
  • Upgrade to higher grade fastener if recommended

Overtightened Components

Symptoms:
  • Cracked or deformed parts
  • Broken fasteners
  • Compressed gaskets or seals
Solutions:
  • Replace damaged components
  • Use new fasteners
  • Follow proper torque sequence
  • Verify correct torque specifications

Diagnostic Steps

Visual inspection, torque verification, thread assessment

1

Visual Inspection

Inspect the affected area for any visible signs of damage or wear

  • Check for cracks or deformation
  • Look for signs of excessive wear
  • Verify proper fastener installation
2

Torque Verification

Verify the torque applied to the fasteners

  • Check the torque wrench calibration
  • Verify the torque specification
  • Compare the applied torque to the specification
3

Thread Assessment

Assess the condition of the threads

  • Check for signs of thread damage
  • Verify the thread type and size
  • Check for proper thread engagement

Prevention Guidelines

Best practices, maintenance tips, tool care

Best Practices

  • Always follow the recommended torque specification
  • Use the correct type and size of fasteners
  • Verify the torque wrench calibration regularly

Maintenance Tips

  • Regularly inspect the affected area for signs of wear or damage
  • Replace damaged or worn-out components promptly
  • Keep the work area clean and organized

Tool Care

  • Regularly clean and maintain the torque wrench
  • Store the torque wrench in a dry and secure location
  • Verify the torque wrench calibration before each use

Frequently Asked Questions

Find answers to common questions about torque specifications

Q1

Why is using the correct torque specification for HVAC components important?

Using the correct torque specification ensures a proper seal and prevents damage to HVAC components. Over-tightening can lead to stripped threads, cracked housings, or damaged gaskets, potentially causing leaks of refrigerant or system malfunctions. Under-tightening can result in loose connections, leading to leaks or vibration issues, which can cause further damage and reduce the system’s efficiency.

Q2

Where can I find the exact torque specifications for my Audi S5 HVAC system?

The most accurate source for torque specifications is the official Audi service manual or repair information system (e.g., ELSAWin). These documents provide the specific torque values for each bolt and fastener within the HVAC system. Accessing this information requires an official subscription or is usually available at a certified Audi service center. Generic manuals may not be correct. It is always recommended to cross reference from multiple sources.

Q3

What happens if I don't have a torque wrench?

Using a torque wrench is highly recommended for any bolt that is critical for sealing an HVAC system. Without a torque wrench, it's easy to under-tighten or over-tighten a fastener, leading to issues previously described. If you don't have a torque wrench, you should consider renting one, taking your car to a professional or purchasing one. It is vital that the repair is done correctly, and that the HVAC system is air tight.

Q4

Are torque specifications for HVAC components usually measured in Nm or lb-ft?

Torque specifications for automotive HVAC components are typically provided in Newton-meters (Nm) or sometimes in pound-feet (lb-ft) in the United States. The Audi service manual will specify the unit for each fastener. Always use the correct unit when applying torque to avoid errors. A conversion calculator is helpful if you need to swap between systems.

Q5

Can I reuse the bolts from the HVAC components after disassembling?

Generally, it is best practice to replace certain bolts, especially those that are self-locking or have a torque-to-yield specification (where they stretch slightly). Reusing these bolts may lead to them not holding correct torque, resulting in leaks. Always consult the official Audi service manual to see if the bolt needs to be replaced.

Environmental Considerations

Temperature, humidity, and seasonal effects on torque specifications

Temperature Effects

Includes: High Heat, Cold Weather, Thermal Cycling

Temperature can significantly impact torque values and fastener behavior

Cold Weather

Effects:
  • Increased material brittleness
  • Higher torque required due to thread contraction
  • Reduced thread lubricant effectiveness
Recommendations:
  • Allow components to warm to room temperature when possible
  • Consider using winter-grade thread lubricants
  • Check torque values more frequently during winter months

Hot Weather

Effects:
  • Thermal expansion of components
  • Decreased friction in threads
  • Accelerated lubricant breakdown
Recommendations:
  • Check torque when components are at normal operating temperature
  • Use temperature-resistant thread lockers
  • Consider re-torquing after heat cycles

Humidity and Corrosion

Covers: Rust Prevention, Salt Exposure, Moisture Control

Moisture and corrosion can affect fastener integrity and torque values

High Humidity

Effects:
  • Accelerated corrosion formation
  • Reduced friction coefficient
  • Potential thread seizing
Prevention:
  • Use corrosion-resistant fasteners
  • Apply appropriate anti-seize compounds
  • Maintain proper protective coatings

Salt Exposure

Effects:
  • Rapid corrosion development
  • Thread damage
  • Seized fasteners
Prevention:
  • Regular underbody washing
  • Use of sacrificial anodes where appropriate
  • Application of protective coatings

Seasonal Maintenance

Spring, Summer, Fall, and Winter maintenance schedules

Spring

  • Inspect for winter damage
  • Clean and protect exposed fasteners
  • Check torque on critical components

Summer

  • Monitor heat-affected components
  • Check expansion-related loosening
  • Inspect cooling system mounts

Fall

  • Prepare for winter conditions
  • Apply corrosion protection
  • Verify all fasteners are properly torqued

Winter

  • More frequent inspection of critical fasteners
  • Check for salt damage
  • Monitor suspension component torque

Related Resources

Tools, service procedures, and technical bulletins

Recommended Tools

Torque Wrench (1/4" Drive)

A 1/4" drive torque wrench capable of measuring torque in Newton-meters (Nm). Necessary for accurately tightening smaller bolts in the HVAC system.

  • Range: 5-25 Nm
  • Click-type mechanism
  • Calibrated for accuracy
Learn more

Torque Wrench (3/8" Drive)

A 3/8" drive torque wrench capable of measuring torque in Newton-meters (Nm). Used for tightening larger bolts found in the HVAC system.

  • Range: 20-100 Nm
  • Click-type mechanism
  • Calibrated for accuracy
Learn more

Socket Set (Metric)

A comprehensive set of metric sockets in 1/4" and 3/8" drive sizes. Needed to fit the various bolt head sizes in the HVAC system.

  • Sizes ranging from 6mm to 19mm
  • 6-point design
  • Chrome vanadium steel
Learn more

Extension Bars (1/4" and 3/8" Drive)

Various length extension bars for accessing bolts in tight spaces within the HVAC system.

  • Various lengths available: 3, 6, 10 inches
  • Durable chrome finish
  • Ball detent design
Learn more

Universal Joint (1/4" and 3/8" Drive)

A universal joint for reaching bolts at angles that can't be directly accessed.

  • Smooth rotational movement
  • Chrome finish
  • Durable construction
Learn more
Service Procedures

HVAC Compressor Bolt Tightening Procedure

This procedure outlines the correct method for tightening the compressor mounting bolts on a 2017-Present Audi S5.

  • Locate the HVAC compressor mounting bolts.
  • Using the correct socket, attach the socket to the torque wrench.
  • Tighten all bolts to 25 Nm in a cross pattern for even distribution of torque.
  • Verify that all bolts are torqued to the specified torque value.
  • Double check your work to ensure that nothing has been missed.
View full procedure

Condenser Mounting Bolt Tightening Procedure

Procedure to properly tighten the bolts that secure the condenser to the vehicle.

  • Locate all mounting bolts for the condenser.
  • Attach the correct socket to the torque wrench.
  • Tighten all bolts to 10 Nm. Do not overtighten.
  • Double check your work to ensure that nothing has been missed.
View full procedure

Evaporator Core Housing Bolt Tightening Procedure

Step-by-step instructions on how to tighten bolts related to the HVAC evaporator core housing.

  • Locate the bolts securing the evaporator core housing.
  • Using the correct socket, attach to the torque wrench.
  • Tighten the evaporator housing bolts to 8 Nm.
  • Verify correct torque setting on all bolts.
  • Double check your work to ensure that nothing has been missed.
View full procedure
Technical Service Bulletins

HVAC Compressor Mounting Bolt Loosening Issue

2019-06-15

Some 2017-2018 Audi S5 models have reported issues with HVAC compressor mounting bolts loosening over time due to improper torque from the factory.

2017-2018 Audi S5

Resolution: Inspect all HVAC compressor mounting bolts. Torque all bolts to 25 Nm according to the service manual instructions. Use a new set of bolts if necessary.

Condenser Mounting Bolt Corrosion

2020-11-20

Several 2017-2020 Audi S5 models have shown signs of corrosion on the condenser mounting bolts due to environmental factors, leading to potential leaks.

2017-2020 Audi S5

Resolution: Inspect condenser mounting bolts for corrosion, replace corroded bolts with new ones, and apply a small amount of anti-seize compound to the new bolts before tightening to 10 Nm.

Evaporator Housing Leakage due to under-torqued fasteners.

2022-02-10

Reports indicate that some 2019-2021 Audi S5 vehicles may exhibit issues of under-torqued fasteners causing leaks in the evaporator core housing. These leaks can lead to reduced HVAC performance and system malfunctions.

2019-2021 Audi S5

Resolution: Inspect all evaporator core housing bolts. Tighten all bolts to 8 Nm. Use new fasteners if necessary. Retest the HVAC system for proper performance following the service manual instructions.

About the Author

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Alan Montanye - Automotive Technical Specialist
ASE

Alan Montanye

Automotive Technical Specialist

ASE Master Certified Technician with over a decade of hands-on experience in automotive repair and diagnostics.

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