AC Servicing Guide En

Training Documentation for Maserati Service Network

A/C System Servicing

Handling and safety guidelines for servicing air conditioning systems in motor vehicles

October 2010

Maserati Academy

A/C System Servicing Introduction

Introduction

It is hard to imagine today’s automobiles without the level comfort added by a modern air conditioning system. Not only do A/C systems keep the cabin temperature at a requested value, one of their main tasks is to remove humidity from the cabin air, and thus reduce window misting on a rainy day. They also filter the cabin air from dust and particulates.

The correct maintenance of an A/C system is vital for its long term performance. Even A/C systems that are in good condition will loose their cooling performance over time due to a natural loss of gas. This document gives an overview of the basic principles of A/C servicing that apply on any vehicle.

Working with refrigerants can be dangerous and care must be taken that they are not released into the atmosphere. This document contains simple guidelines for dealing with refrigerants in a safe and responsible manner.

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For any repairs and service operations on Maserati vehicles, please refer to the relevant technical documentation.

The following arguments are treated in this guide:

• A/C System outline p3

• Refrigerant p6

• Compressor oil p8

• Moisture in the system p10

• Servicing air conditioning systems p12

• System diagnosis with pressure gauges p16

• Leak detection p18

• Health and Safety p20

Climate control in motor vehicles is a principal requisite for the driver’s concentration, and to end journeys fresh and relaxed.Correct maintenance however is vital for the long term performance of any A/C system.

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A/C System outline

A/C System outline

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1. Low pressure side

2. High pressure side

3. Evaporator

4. Compressor

5. Condenser

6. Dehydrator/ filter

7. Multilevel pressure switch

8. High pressure service valve

9. Low pressure service valve

10. Blower motor blows hot, humid air from the cabin space to the evaporator

11. Cold, dry air from the evaporator entering the cabin space

12. Radiator fan provides fresh air to the condenser

13. Hot air coming out

14. Refrigerant in gaseous state

15. Refrigerant in liquid state

16. Condense water drain

17. Thermal expansion valve

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A typical automotive air conditioning system is made up of the following main components:

Compressor

The compressor is the heart and the driving force of every A/C circuit. It is driven by the engine by means of a poly-V belt and in many cases it can be switched on and off by an electromagnetic clutch. Many types of compressors exist, like piston, scroll and vane compressors; but they all perform the same job: suck vapour from the evaporator, compress this vapour to raise its temperature above the ambient temperature, and pump hot, high pressure vapour to the condenser.

Evaporator

The evaporator is located in the heater/air distribution unit in the cabin space. Its function is to extract heat from the ambient air passing into the vehicle’s interior helped by the blower motor.

The low pressure, liquid state refrigerant entering the evaporator evaporates into gas and absorbs heat during this process.

Condenser

The condenser is located in front of the engine cooling radiator. Its task is to cool down and condense the refrigerant into liquid. During this process, the heat absorbed by the refrigerant in the evaporator is released to the ambient air. This process is helped by the radiator electric cooling fan.

Dehydrator / filter

The dehydrator/filter (also refered to as receiver/drier) protects the A/C circuit by filtering out any debris. It also contains a desiccant substance that absorbs any moisture from the refrigerant passing through it. Different variants of dehydrators/filters are used (separate type or integrated in the condenser body) and usually they can be replaced as a service item.

A/C System outline

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Multilevel pressure switch

The multilevel pressure switch has two functions:

•Protecting the compressor and the circuit from damage caused by a too low or a too high circuit pressure (by swithing the compressor off at pressure below approx. 2,5 bar and above approx. 27 bar)

•Activating the electric radiator fan (1° speed at approx. 15 bar and 2° speed at approx. 20 bar)

Expansion valve

The expansion valve is located at intake side of the evaporator. Its function is to reduce the pressure of the liquid refrigerant. This pressure reduction causes a drastic drop in refrigerant temperature.

The expansion valve also acts as a metering device. It controls the refrigerant liquid flow into the evaporator based on the temperature of the vapour leaving the evaporator (thermostatic expansion valve).

Note: orifice tubes and accumulatorsSome A/C systems use an orifice tube instead of an expansion valve. Orifice tubes have the same function as an expansion valve, but they are fixed instead of self-regulating. Therefore, orifice tube systems use an accumulator between the evaporator outlet and compressor intake (usualy integrated with the dehydrator/filter) to prevent liquid refrigerant from entering the compressor.

A/C System outline

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Refrigerant

What makes a gas suitable for being used as A/C refrigerant?

- A low boiling point.

Can refrigerant be released in the atmosphere?

- No! The refrigerant must be recovered using suitable equipment.

What effect does low pressure have on refrigerant?

- The boiling point is lowered.

What effect does high pressure have on refrigerant?

- The boiling point is raised.

Why is this pressure /temperature relationship so important with refrigerant?

- This characteristic is required to utilise the refrigerant to absorb and release heat when changing state (gaseous / liquid).

Liquid

Gas

Refrigerant

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Refrigerant R12 – Dichlorodifluoromethane

• Boiling point: -29 °C (at 1 bar)

• Used up until 1993

• Replaced by R134a from 1995

• Illegal to service from 2000 (system conversion to refrigerant R134a by specialists).

• CFC – Chloroflurocarbon (Ozone depleting)

• Takes up to 100 years to degrade when released into the atmosphere.

• Unlimited fine and up to 4 years imprisonment for knowingly releasing into the atmosphere (in the UK).

Refrigerant R134a – Tetrafluoroethane• Boiling point : –26,3 °C (at 1 bar)

• Used since 1995

• HFC – Hydroflurocarbon (adds to greenhouse effect)

• Hygroscopic

• Takes up to 13 years to degrade when released into the atmosphere.

• Global warming potential

• Up to £10,000 fine for knowingly releasing into the atmosphere (in the UK).

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Refrigerant

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Compressor oil (PAG)

• Compressor oil for R134a systems is a synthetic lubrication oil, most commonly termed as PAG (PolyAlkyleneGlycols) oil.

• PAG oils are extremely hygroscopic.

• As air contains moisture, airtight containers should be used to store the oils.

• Never mix different types of PAG oils.

• Never reuse discharged oil.

• Always wear gloves when handling the oils.

• As there are several different makes and styles of compressors it is important that the correct viscosity oil is used to prevent component damage.

• The oil used in the compressor lubricates the whole system so it is important that the correct amount of oil is used.

• When replacing any components of the A/C system, oil will be lost from the system, therefore it is necessary to replace this lost oil with a specific amount depending on the component being changed.

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Compressor oil

Refrigerant cylinder transportation and storage

• Store and transport refrigerant cylinders in an upright position.

• Store out of direct sunlight.

• Place sealing cap on outlet valve to prevent thread damage, contamination and refrigerant leakage.

• Never allow cylinder temperature to exceed 50oC. This could result in excessive cylinder pressures and damage the containers integrity.

• Do not allow the cylinders to become to cold (keep them inside during winter time).

• Keep the cylinders in their original packaged carton thus preventing damage to the cylinder such as dents, punctures or scratches.

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Component Amount of oil to be added

Evaporator 50 ml

Condenser 30 ml

Dehydrator / filter 10 – 20 ml

Piping 10 ml

Oil to be added in case of component replacement (these figures are indicative only and depend upon the vehicle):

Replacing a compressor:

New compressors contain the full amount of oil required by the system. Therefore, when replacing the compressor, first drain and measure the amount of oil contained in the old compressor. Then, drain the new compressor, and pour the same quantity of oil that was removed from the old compressor, plus an additional 20 ml, into the new compressor.

For compressors follow the instructions supplied with unit!

The manufacturers recommended PAG Oil (ISO Type) should always be used so as not to risk invalidating any warranty terms and conditions.No compressor manufacturer allows the use of a universal oil!

PAG oil is highly hygroscopic! Oil must come from a sealed container that has not be opened to air

before use (air contains moisture)!

CAUTION

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Compressor oil

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Moisture in the system

It does not:• Flush a system• Unblock a system• Restore the dryer or accumulator• Remove oil

Its only purpose is to remove:• Air• Non-condensable gases• Moisture

R134a and the oils associated with it cannot tolerate moisture, as they are extremely hygroscopic.

Once the A/C a system is saturated with moisture, irreparable damage is done to the interior of the system. If the moisture condition is neglected long enough, pinholes caused by corrosion appear in the evaporator and condenser coils and in any metal tubing used in the system. Any affected parts must be replaced.

In addition, aluminium parts can become so corroded that the compressor is unserviceable. Valves and fittings can be so severely damaged that they are no longer usable.

Further, moisture can in certain conditions generate icing. This will lead to poor performance caused by expansion valve blocking and possible damage to the compressor.

Where there is. evidence of moisture in a system, a thorough clean out is recommended. Such a clean out should be followed by the installation of a new dehydrator / filter and a complete system vacuum carried out.

There is only one reason for vacuuming an air condictioning system and that is to make sure it is dry and free from moisture.


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For all practical purposes, refrigerant can be considered to be moisture free. The moisture content of new refrigerant should not exceed 10 parts per million (10 ppm) of refrigerant.

Whenever a component is removed from the system for repair or replacement, air is introduced into the system. As a result of this, there is always a danger of moisture entering the unit since air contains moisture.

Refrigerant absorbs moisture readily when exposed to it. To keep the system as moisture free as possible, all A/C systems use a receiver/dryer or an accumulator, which contains a bag of desiccant such as silica gel. Desiccants are able to absorb and hold a small quantity of moisture.

Any water introduced into the system in excess of the amount that the desiccant can absorb is free to travel around the system. Even one drop of free water that cannot be controlled causes irreparable damage to the internal parts of the A/C system.

Moisture in concentrations greater than 20 ppm can cause serious damage. To illustrate how small an amount 20 ppm is, one small drop of water in an A/C system having a capacity of 700g amounts to 40 ppm, or 3 to 4 times the amount that can be tolerated.

Moisture in the System


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A/C service equipment

Servicing air conditioning systems

Why is it necessary to service automotive air conditioning systems?

- System performance degrades over time due to natural loss of gas in the circuit. The dehydrator / filter will usually have a service life too.

What are the basic operations required for air conditioning system repair or service?

- Perform the steps in the following order:

1.System test

2.Refrigerant identification

3.Refrigerant recovery

4.Vacuum and leak detection

5.Charging refrigerant

6.Final system test and leak check

Servicing A/C systems

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Good working practice•When servicing an air conditioning system, always install the dehydrator/filter last.•When servicing any air conditioner parts, always cap the open ends of the hoses and fittings immediately.•Never work around water, outside in the rain, or in very humid locations.•Do not allow new refrigerant or refrigeration oil to become contaminated.•Always keep the refrigeration oil container capped.•Develop clean habits; do not allow dirt to enter the system.•Keep all service tools free of grease and dirt.•Never fill a unit without first ensuring that air and moisture are removed.

Required every 1-2 years• Check the cabin temperature at air vents.• Check drive belt tension and condition – change if required.• Check condition of hoses and fittings.• Reclaim refrigerant and check quantity of gas in the system • Change dehydrator/filter at defined time by service schedule • Vacuum 45 minutes and recharge the system.• Change cabin air filter.• Run system and check temperatures & pressures.• Microbiologically clean the system.

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Change dehydrator/filter

Dehydrators/filters are there to absorb corrosion causing moisture and to filter any particulates that are circulating around in the system.

What particulates can be found in an air conditioning system?

Rust• If moisture has been present in a system for a period of time, rust could be formed

on any metal parts. This rust can flake and be transported around the system by the refrigerant.

Metallic particles• If the compressor seizes and fails it could start to break up internally, and these bits

could find there way around the system.

Silica gel granules• The drying agent in the dehydrator once totally saturated, turns to mush and can

circulate around the system.

Grease and general debris• If a system has been opened for a repair and the filter has not been replaced,

general workshop debris could enter the system.

In case the A/C circuit has been exposed to the outside air for more than a few hours, or there are other reasons to

suspect contamination, the dehydrator / filter must always be replaced!

CAUTION


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Due to the damp conditions surrounding the evaporator bacteria and mould develop.

The air from the dash vents will start to smell.

Microbiological cleaning

Microbiological cleaning of the ventilation system every 1-2 years can prevent this. Follow the handling instructions supplied with the product.

Cabin air filters

These are also known as pollen or micro filters.

Two types can be distinguished:

•Fibre (usually white colour)

•Activated Carbon (dark grey colour)

Function:

• All incoming air is drawn through the filter.

• Clean air is then passed into the vehicle.

• Fibre type filters only filter dust and pollen.

• Activated Carbon type filters are the most effective; they also filter chemical gasses, cigarette smoke and other odours.

• The filter should be changed as per manufacturers instructions, or more frequent in dusty circumstances.

• Too dirty filters will affect the effectiveness of the A/C system.

• It is not recommended to replace a filter with one of a different type.


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Vacuum for 45 minutes before recharging the system!

Vacuuming the system

A good vacuum pump is capable of evacuating a system to a pressure of minus 100.6kPa or better.

At this negative pressure, water boils at 4.4°C. In other words, if the ambient temperature is 4.4°C or higher, water boils and is drawn out of the system by the vacuum pump.

Removal of moisture from a system can be compared to the boiling away (vaporisation) of water in a saucepan. It is not enough to cause the water to boil; time must be allowed for the water to boil away completely.

How long vacuuming is long enough?

- Until the vacuum gauge does not fall back!

00

Vacuum held = ok

00

Vacuum falls back to zero: Suspect a vacuum leak

00

Vacuum partially falls back:Moisture has not fully boiled off


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System diagnosis with pressure gauges

Low pressure side

2kg/cm2

High pressure side

15kg/cm2

A manifold gauge set can be used or pressure gauges integrated in an A/C service station. The method is identical in both cases. The pressures below are indicative only and can vary slightly due to ambient temperature variations.

Test conditions:

•Start the engine and bring it to normal temperature.

•Open all the vehicle’s doors.

•Set the blower motor to maximum speed.

•Set the temperature control to maximum cool position.

•Run the engine at about 1500 rpm.

Normal condition:

• The cooling performance will be maximum.

• Low pressure side: 1,5 – 2,5 bar.

• High pressure side: 14 – 16 bar.

System overcharged:

• Reduced cooling performance.

• Too high system pressure at both sides.

• Compressor will be noisy.

• Risc of system damage.

• Excessive refrigerant: recover the circuit and charge with the correct amount.

• Check the electric fan operation.

Low pressure side

2.5kg/cm2

High pressure side

23kg/cm2

System diagnosis

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Low charge – circuit leakage:

• Reduced cooling performance.

• Too low system pressure at both sides.

• Bubbles seen in sight glass continuously.

• Insufficient refrigerant: recover the refrigerant.

• Perform a leak check before charging the system.

Low pressure side

0.8kg/cm2

High pressure side

8~9 kg/cm2

Ice in the system:

• Periodically cools, then fails to cool.

• Pressures sometimes normal and sometimes too low.

• Icing in the circuit causes the expansion valve to block sometimes.

• Oversaturized dehydrator.

• Replace dehydrator and carefully vacuum the system before recharging.

Low pressure side

50cmHg~1.5 kg/cm2

High pressure side

7~15kg/cm2

Low pressure side

76cm/Hg

High pressure side

6kg/cm2Blockage in the system:

• Poor cooling performance.

• Pressure too low at both sides.

• Frost on the tube to the dehydrator/filter.

• Blocked filter element, dehydrator/filter must be replaced.

System diagnosis

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Leak detection

Ultra Violet dye injection

An ultra violet dye is injected into a system charged with refrigerant. The A/C system is then run for a period of time. Any leak will allow the dye to escape with the refrigerant. By directing a UV light around suspect areas, and the user wearing the correct yellow glasses, a leak will be seen as a luminous green stain.

Electronic leak detection

An electronic refrigerant detector is sometimes called a “Sniffer”. Ensure batteries are in good order and the tip is free from oil and dirt. Carefully pass the tip around all pipes and pipe joints, especially on the lower side. If a leak is detected the tone will speed up.

Leak detection

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A/C System Servicing Leak detection

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Pressurise with Oxygen Free Nitrogen (OFN)

This is one of the legal methods of pressurising an A/C system for the detection of leaks. Using refrigerant is not legal! You must not knowingly vent refrigerant to the atmosphere.

How to check an A/C system using OFN?

•Recover any refrigerant from A/C system before starting.

•Introduce Nitrogen via a suitable adaptor into the service valves up to a maximum of 15 bar. Always use a regulator and never exceed 15 bar.

•Do not run the A/C whilst pressurised with Nitrogen.

•Leak check with UV or a proprietary bubble dye solution.

•Wait at least 30 minutes and check the low pressure gauge: the allowable drop is zero!

•Release OFN before any further work.

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Personal Protection Equipment (PPE)

Always wear the correct PPE whilst working with refrigerants.

Health and Safety

Health and Safety

Fluoroelastomer gloves

• These are the only suitable gloves for safe working on A/C systems.

• Do not use fabric gloves, latex gloves etc.

Safety goggles

• Refrigerant in contact with the human eye will freeze the eyeball (- 26,3 °C) leading to blindness!! Ensure box type goggles are used.

• Safety glasses do not provide sufficient protection!!

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Safety precautions

1. Work in a well ventilated area. Refrigerant is heavier than air – it would collect in the bottom of a pit! Avoid laying on the floor as refrigerant is heavier than air. In case of accidental leakage vent the workshop.

2. Do not allow the refrigerant cylinders to overheat - Keep well below 50ºC.

3. No naked flames (R134a will burn at 93°C creating a toxic gas).

4. Do not leave refrigerant cylinders outside either – avoid them getting too cold.

5. Wear suitable protective clothing (PPE as well as overalls and safety shoes)!

6. Avoid skin contact with liquid refrigerant (risk of local cold burns, or worse still Frost bite – the boiling point of R134a is -26.3°C!).

7. Do not inhale cryogen vapours in high concentrations. Note: they displace the oxygen in the air you breathe.

8. Do not expose refrigerant to smoke or fire as it will produce toxic gasses – this can be detected by a pungent smell.

9. Provide adequate workplace ventilation if high concentrations are likely to occur!

10. Prior to welding and brazing on AC systems, remove the cryogen and blow out any remaining traces with nitrogen.

11. Vehicles being placed in spray ovens reaching above 80°C should have the refrigerant recovered.

• In case of contact with eyes or mucous membranes, wash immediately with copious amounts of flowing water and consult an eye specialist!

• In case of skin contact, remove affected clothing immediately and wash skin areas with copious amounts of water.

• If high concentrations of cryogen vapours are inhaled, immediately move the affected person into the fresh air and call for a doctor.

• In case of breathing difficulties administer oxygen. If the affected person's breathing is faint, or has ceased altogether, bend his head backwards and provide mouth-to-mouth resuscitation. – Trained and competent person only, designated First Aider!

• Refer to Material Data Sheets.

First aid instructions

Health and Safety

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Maserati Academy – October 2010

MASERATI reserves the right to make any modification to the vehicle models described in this manual, at any time, for either technical or commercial reasons. All rights reserved. This document may not be reproduced, even

partially, without the written consent of Maserati S.p.A.

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AC Servicing Guide En

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