Climate Units - Design and Function (Convertible): Other Volvo C70 I

Reading off input and output signals

Using this function the values and status of the control module input and output signals can be continuously read off.

The following parameters can be read off

1. generator (GEN) voltage D+, status
2. blower fan switch, position
3. air distribution selector, position
4. left temperature control selector, position
5. right temperature control selector, position
6. REC buttons, status
7. A/C-buttons, status
8. Damper Motor Position Sensor recirculation, position
9. Damper motor air distribution position sensor, position
10. damper motor position sensor temperature driver side, position
11. damper motor position sensor temperature passenger side, position
12. sun intensity, value
13. passenger compartment temperature, value
14. engine coolant temperature (ECT), value
15. outside temperature, value
16. time since ignition on, value
17. vehicle speed, value
18. fan passenger compartment temperature sensor, status
19. communication power unit blower fan motor, status
20. control module control of blower fan, value.

Reading off programming data

This function can be used to read off programmed data and program data into the control module. The purpose of the programming is to adapt the control module to the car version or when the driver requests that certain adjustments are made to the settings.

Note. Before replacing a control module all programmed data must be read off first if this is possible. The information will then be downloaded into the new control module after it has been installed.

The following data can be programmed into the control module or read from it

1. driver position (which side of car driver sits, left-hand or right-hand drive car)
2. engine type (indicates if car has gasoline or diesel engine).
3. passenger compartment ventilation filter (indicates whether the climate control system has a passenger compartment ventilation filter)
4. passenger compartment temperature (adapts passenger compartment temperature in relation to the selected position on the passenger compartment temperature selector).
5. blower fan speed (adapts blower fan speed control when the blower fan switch is in the AUT position).

Note. A new control module must be programmed with the driver's position, if it isn't the green LEDs in the REC and AC buttons will flash and the climate control system will not be accessible to regulate the climate in the passenger compartment. After programming the driver position, it is necessary to carry out self-adjustment of the damper motors.

Scheme 397

This service initiates self-adjustment of the climate unit damper motors.

Note. For self-adjustment of the damper motors the engine must be running at idle (generator (GEN) charging).

Summary

The role of the air conditioning system is to increase comfort and traffic safety.

The air conditioning expels heat but does not produce coolness.

The air conditioning operation principles are the same for all systems. There are some differences in detail depending on the type of system (expansion pipe/TEV valve).

The principle differences between the various cars is how the climate in the car is controlled, manually or automatically (MCC, ACC, ECC). Climate control is treated as a separate subject.

If you understand how the air conditioning system functions makes it easier to quickly diagnose correctly any fault.

If you understand how the air conditioning system operates you also understand how important it is that work on these systems is carried out correctly.

Scheme 398

A/C Stations And Equipment

A/C stations

To satisfy the legal requirements and to allow rational handling, Volvo has developed A/C stations which can be used to

1. empty the system and clean and recycle refrigerant.
2. vacuum pump, check seals and top up the system.

The instructions for service and maintenance of the A/C station must be followed carefully so in order for it to function correctly.

Draining the system

The system (car) should have a temperature of at least 20°C (68°F). In cold climates the car should be taken into the workshop the evening before the work will be carried out.

The drainage time is reduced if the A/C system has recently been running and the engine is hot (radiant heat).

Vacuum pumping, leak testing the system

Any topping up of the oil in the system must be carried out prior to vacuum pumping.

This primary aim of vacuum pumping is to evacuate any moisture from the system. The low pressure means that the water evaporates and can then be sucked out of the system.

To ensure that all moisture is removed from the system, it is important that vacuum pumping continues for at least 50 minutes . In humid climates this may take even longer .

This other reason for vacuum pumping is to check that the system is sealed. When pumping is complete, the negative pressure may only be reduced minimally for approximately four minutes.

Topping up the system

Fill with the correct amount of refrigerant (the amount depends on the car and model year etc).

Too much refrigerant reduces the capacity. In addition there is a risk off refrigerant in liquid form reaching the compressor with increased wear/incidence of breakdown as a result.

Too little refrigerant reduces the capacity. In addition there is a risk off poor compressor lubrication (lack of oil) with increased noise/wear/incidence of breakdown as a result.

Leakage test

In addition to the vacuum method (vacuum pumping) a supplementary test must be carried out with a leakage locator after the system has been opened.

Note. The leakage locator must be adapted for refrigerant.

On hoses with PVC casing the casing must be removed and the hose with connections must be wiped clean prior to leak tracing.

This is because refrigerant diffuses (= forces its way out) through the hoses. The small amount that forces its way out is then collected under the casing and this amount may be sufficient to affect the leakage locator.

Performance test

After the system has been opened, a performance test must be carried out to check the function of the system and its capacity.

Scheme 399

Air conditioning system tasks

The air conditioning system has two main tasks

1. to lower the air temperature in the passenger compartment to a comfortable level.
2. to dehumidify the air (reduce the humidity) that enters the passenger compartment.

Note that the air conditioning expels heat but does NOT create coolness.

The air conditioning is a contained system filled with refrigerant and in principle its function is the same as a normal refrigerator

1. an evaporator which takes the heat from the air and dehumidifies the air.
2. a condenser in which the removed heat is transferred to the air.
3. in addition there is a compressor and a number of other components in the system.

Lowered passenger compartment temperature - increased traffic safety

It is well documented that the human performance abilities are reduced in heat. Research carried out in traffic and in a normal car demonstrated that when the passenger compartment temperature is increased from 21 to 27°C (70 to 81°F)

1. the risk of the driver missing important traffic information (hazard warnings, traffic signals, signs etc.) increased by 50%.
2. driver reaction times where 22% slower.

With an air conditioning system, car travel is both more comfortable and safer.

Dehumidified air feels cooler

Sweat evaporates much more quickly if the air is dry. The skin then feels dry and therefore more comfortable.

When the air entering the passenger compartment encounters the cold evaporator, the humidity in the air condenses on the evaporator. The water drains out under the car via a drain hose. In the event of high humidity, this may be considerable quantities of water, which is often mistaken for a water leak from the engine for example.

The water which condenses binds and takes with it some of the dust and the larger impurities in the air. Therefore the air conditioning system also helps to purify the air.

Scheme 400

There are five main components in the system

1. evaporator
2. receiver drier
3. compressor
4. condenser
5. choke valve.

The system is filled with a suitable quantity of refrigerant and oil.

The system has both a low and high pressure side. These are divided by the compressor and the choke valve.

The evaporator is located on the low pressure side and the condenser is on the high pressure side.

The air conditioning system functions only at outside temperatures above approximately 0-5°C (32-41°F) (varies depending on the type of system). At lower temperatures the pressure in the system is too low and the compressor is not engaged.

Evaporator (=air heated heat exchanger)

In the evaporator the heat is transferred from the warm air (the heat is "cooled") to the cold refrigerant.

The refrigerant then begins to boil and is converted to gas form (evaporates).

The blower fan increases the air flow through the evaporator.

Note. In most systems, the blower fan must be operating before the air conditioning system can be engaged.

Receiver drier

The receiver drier has a number of tasks, such as collecting and binding the moisture (water) in the system.

The receiver drier is located on either the low pressure or the high pressure side, depending on the type of system.

Compressor

Sucks refrigerant in gas form from the evaporator.

Compresses the refrigerant thereby increasing its pressure and temperature. The heated refrigerant in gas form passes on to the condenser.

Condenser (= air cooled heat exchanger)

At the condenser, the heat is transferred from the refrigerant to the colder outside air.

The refrigerant then condenses and changes into liquid form.

In most systems there is an electrical fan which increases the air flow through the condenser. This increases the transfer of heat from the refrigerant to the outside air. This of course also increases the capacity of the air conditioning system.

Choke valve

Downstream of the choke valve is the refrigerant in liquid form at high pressure.

The choke valve regulates the amount of refrigerant that flows into the evaporator.

Scheme 401

Impact of refrigerant on environment

At the beginning of the 1930s it was believed that the perfect refrigerant had been discovered - different CFC components. Later research demonstrated that CFC (for example R12) severely affects our environment.

Due to this, a less aggressive refrigerant has been developed - different HFC compounds (for example R134a). In addition there are now a number of international agreements, national legislation and directives that govern the use of refrigerants.

Initially CFC compounds were called Freons. But Freon is in fact only the name of a product from a manufacturer.

Later there was international agreement about a R code for refrigerants. The letter R is for refrigerant and the number that follows it indicates the chemical compound.

The effect of refrigerants on the environment is usually listed in ODP and GWP.

ODP = Ozone Depleting Potential.

GWP = Global Warming Potential.

Note. The value R11 is used as the starting point to assess the effect on the environment. ODP and GWP for R11 are given as 1.

The ozone layer around the earth

Sunlight contains a lot of energy rich short wave radiation (ultraviolet radiation) which is damaging to all living cells. The ozone layer in the stratosphere, 15-40 km (9-25 miles) above the earth, catches almost 99% of the dangerous ultraviolet radiation.

The ozone molecule is unstable and consists of three oxygen atoms (O3). Ozone is consumed and renewed constantly, it is regenerated by sunlight.

Human emission of chlorine etc (which is in R12) breaks down the ozone layer quicker than it can regenerate. This leads to what are called holes in the ozone layer, which are in reality areas where the ozone layer is thinner.

Thinner ozone layers result in increased ultraviolet radiation which causes greater damage to all living cells, both animal and plant.

Some examples of this are

1. increased incidence of different forms of skin cancer.
2. increased incidence of eye damage (for example cataracts and what is known as snow blindness).
3. damaged vegetation (amongst other things worsened growth/harvests).
4. damage to marine life (for example killing of algae, poorer quality vegetation and fish).

Green house effect

Sunlight which is a short-wave energy rich form of radiation reaches the earth. Most of the sunlight is reflected towards the earth and bounced back to space as longwave heat radiation. Some of this heat radiation is reflected back towards the earth by gases (= greenhouse gases) in the atmosphere. This phenomenon is usually known as the greenhouse effect.

The greenhouse has existed since the atmosphere was created and it this gives us a tolerable temperature on the earth. Without the greenhouse effect the average temperature of the earth would be approximately -18°C (0°F) instead of the present approximately 15°C (59°F).

The human way of life, in particular during the last 30 years, has considerably increased the emission of greenhouse gases into the atmosphere (for example carbon dioxide, methane, NOx, CFC).

This results in the gas layer in the atmosphere becoming thicker - and therefore more heat is reflected back to the earth, causing the average temperature of the earth to rise. In other words, the greenhouse effect is increased.

The consequences of an increased greenhouse effect are a subject of much discussion, but without doubt it damages the climate balance of the earth.

Scheme 402

A refrigerant needs to fulfill a number of important requirements. Amongst other things, it must be able to mix with oil and be non-corrosive. This is to provide good compressor lubrication and to prevent the metals and seals in the system from deterioration.

In older Volvo cars, R12 (CFC compound) is used as refrigerant. But in newer cars this has been changed to R134a (HFC compound) for environmental reasons. In addition, kits to convert and adapt older cars for R134a have been developed.

There is a decal on, or in the vicinity of, the receiver drier. The color of the decal indicates which types of refrigerant and oil the system is filled with.

Notes

1. PAG = Poly Alkylene Glycol Different PAG oil depending on the compressor.
2. Black = early version, Blue = late version.
3. Green = may only be used for S40/V40.

Conversion from R12 to R134a, "Retrofit"

Conversion kit contents

The contents of the kit vary depending on the car and model year, but in all cases ester oil, a receiver drier and an expansion pipe or a TEV valve is included.

For certain cars, in addition to the basic kit there are also one or more supplementary kits (pipes, shaft seal for the compressor).

The cooling performance is unchanged by the conversion.

Why replace the oil and components?

Mineral oil which is used for R12 does not mix with R134a. Most of the mineral oil must therefore be replaced with ester oil. Ester oil can be mixed with both R134a and the remaining mineral oil in the system. In addition it has little effect on the material in the O-ring. As a result, only the O-rings on the connections that are opened in order to replace a component require replacing.

Note. On Sanden 508-510 and 709 compressors the shaft seal must be replaced with a seal adapted for R134a. This also applies when a replacement compressor is being used in a converted system.

The receiver drier must be replaced because

1. the drying agent intended for R12 becomes chemically unstable and brakes down if it is exposed to R134a.
2. sufficient service life can be obtained (the old drying agent by may have consumed a quantity of water).

Expansion pipe/TEV valve must be replaced to obtain the correct flow of refrigerant (the molecules in R12 are larger than in R134a).

Scheme 403

All subjects are made up of molecules (molecule = a group of atoms).

If a drop of water, for example, is disturbed, it is possible to see how the molecules move rapidly about inside the drop.

The higher the speed of the molecules, the greater the movement energy they have.

What is called heat is a result of this kinetic energy that the molecules have temporarily.

The extent of the kinetic energy can be gauged directly with a thermometer.

Heat is a form of kinetic energy.

Little kinetic energy (the molecules move slowly) = low temperature.

High kinetic energy (the molecules move rapidly) = high temperature.

There are a number of different ways (different scales) to list the temperature.

Scheme 404

The temperature scales have different starting points and are named after their inventors.

Celsius and Fahrenheit

The scales have a zero point and are graded in both plus and minus degrees.

The thermometer reading is a measurement of the kinetic energy of the molecules (= the heat).

Because there is a thermometer reading also at minus grades, the molecules cannot have already stopped moving (heat be zero) at 0°

In terms of pure physics, it is also incorrect to talk about warm and cold grades. Put simply, different temperatures correspond to different levels of heat.

Celsius took water as a starting point when he made his scale.

The boiling point of water was set at 100° and the freezing point at 0° on his scale.

Fahrenheit cut his finger and used both his blood temperature and a refrigerated mixture of ice and salt as his starting points.

The temperature of his blood was set at 100° and the frozen mixture's temperature was set at 0° on his scale.

Conversion between Celsius and Fahrenheit

C = ((F-32) x 5) / 9

F = (C x 9) / 5 + 32

Kelvin

This scale is based on the kinetic energy of the molecules.

0° K = absolute zero = the molecules have stopped moving completely.

Scheme 405

Heat exchange can take place in three ways

1. Through radiation. Heat radiation does not depend on a material to transfer the heat. The heat of the sun for example reaches us through radiation.
2. By conduction. The heat is transferred via contact between different bodies.
3. By convection. The heat is transferred via a liquid or a gas.

Heat exchange often takes place through a combination of these methods.

For example as in the illustration

1. the heat from the sun is transferred via radiation to a metal post
2. from the metal post to the water by conduction
3. from the water to the container by convection

Heat transfer can only take place in one direction

Heat is always transferred from an object with a higher temperature to an object with a lower temperature.

The greater the temperature difference, the quicker the transfer of heat.

If a beaker with cold water is placed in a beaker with heated water, the heat will be transferred from the beaker with hot water until the temperature is the same in both beakers.

As the temperature difference between the two beakers reduces, the heat transfer slows down.

Scheme 406

Evaporation

As the heat is transferred to the water, the temperature of the water increases successively. However water cannot receive and store infinite quantities of heat.

At approximately 100°C (212°F) and normal air pressure, the water cannot consume any more heat.

If the supply of heat to the water continues, the water will give off as much heat as it is supplied with.

The water disposes of the excess heat by converting to steam. As long as there is still water, the temperature remains at 100°C (212°F) in both the boiling water and in the steam.

Eventually all the water will evaporate.

If further heat is applied to the steam, its temperature will rise (= super heated steam).

Note. Do not confuse the amount of heat and the temperature. For example a burning match has a temperature of approximately 600°C (1112°F), but gives off little heat; possibly enough to heat the water in a thimble a couple of degrees.

Condensation

If the supply of heat is removed, the steam will condense into water after a while.

This is because the heat is transferred from the hot steam to the cooler surrounding.

During condensation, as much heat is released as was consumed during evaporation.

Quantity of heat

Different amounts of heat are required to raise the temperature of the water, to evaporate the water, to super heat the steam and to condense the steam into water.

If, for example, we have a certain amount of heat which we will call 1 unit it would be as follows

1. 1 unit to increase the temperature of the water from room temperature (20°C (68°F)) to boiling point.
2. 7 units to convert the boiling water to steam.
3. 0.45 units to super heat the steam.
4. 7 units to condense the steam to water.

Most heat can also be transferred when the water changes from one state to another.

This applies to all liquids, including refrigerants.

This is one of the reasons that it is so important that the amount of refrigerant in the air conditioning correct.

1. Too much refrigerant in the evaporator the refrigerant heats up but evaporates only partially a smaller amount of heat is taken from the air leading to reduced capacity.
2. Too little refrigerant in the evaporator the refrigerant evaporates and the steam is super heated a smaller amount of heat is taken from the air reduced capacity.

Scheme 407

Evaporation temperature, condensation temperature

The temperature at which a liquid begins to boil depends not only on which liquid it is, but also on the pressure.

Water for example, begins to boil and evaporate at 100°C (212°F) at normal air pressure (÷ 1 bar).

In order for the water to be able to boil and evaporate, the pressure of the steam must be higher than the air pressure.

This means that if the air pressure is increased, the boiling point also increases. Conversely of the pressure is reduced, the boiling point is lowered.

For example water boils at

1. 180°C (356°F) if the pressure is 10 bar.
2. 20°C (68°F) if there is a negative pressure of 0.97 bar.

Changes in volume

The following applies to all gases

1. when the volume is reduced, pressure and temperature increases.
2. when the volume is increases, pressure and temperature is reduced.

A change in volume also effects the evaporation and condensation temperatures.

Scheme 408

If two beakers, a compressor and a choke valve are connected together as illustrated, it is a contained system.

The compressor and the choke valve divide the system in to a low pressure section and a high pressure section.

Without the choke valve the compressor would only function as a pump.

Function

The choke valve governs the quantity of liquid that is released up to the right beaker. The quantity of liquid must be so much that the final remains of the liquid evaporate precisely before the beaker spout. Too little or too much liquid means that the amount of heat that can be taken up reduces.

The compressor lowers the pressure and the temperature in the right beaker. The liquid in the beaker then boils and evaporates at low temperature. This results in the temperature difference between the flame and the liquid becoming greater and the heat transfer from the flame to the liquid becomes quicker and more efficient.

The compressor extracts the gas from the right beaker, increases the pressure of the gas and temperature and presses out the gas in the left beaker. As a result the temperature difference between the gas and the ambient temperature becomes great. The gas then condenses at a high temperature and the heat transfer from the gas to the air becomes rapid and efficient.

Scheme 409

The control module has a built-in diagnostic system, the Volvo on-board diagnostic (OBD) system, which continuously monitors itself and its input and output signals.

Read off and erase the low current protection status

With this option the low current protection status can be read off and erased.

The control module uses the low current protection to interrupt or shut off the additional heater while running if the control module registers that the power supply is too low.

Using this function the values and status of the control module input and output signals can be continuously read off.

The following parameters can be read off

1. battery voltage, value
2. outside temperature, value
3. coolant temperature, value
4. additional heater, status
5. ignition supply, status
6. generator (GEN) voltage D+, status
7. the status displays whether or not the control module has registered too low power supply.
8. fuel pump (FP), status
9. glowplugs, status
10. water pump, status
11. combustion fan, value
12. timer, status
13. run time, value

Scheme 410

With this option the components/functions in the additional heater system can be activated.

The following components can be activated

1. additional heater.
2. water pump.
3. combustion fan.
4. glow plug.

With this option it is possible to read programmed data and program in data. The aim with this programming is set up the additional heater function according to the customer's requirement.

Note. If possible read off all data from the control module before replacing the control module. After replacement the current data is programmed into the new control module.

The programmable data is the start temperature setting. Start temperature refers to the highest outside temperature at which the additional heater may start.