The Air Conditioning on the 'A' Class is Off (not operating Cooling and dehumidifying) when the indicator located in the centre of the EC switch is ON 1 The re-circulation of air facility is operating when the light in the centre of the switch is ON as seen in
Air Flow control
Temperature Selector Control (C)
Air Distribution Control. (D)
Air re-circulation switch (E)
Air Conditioning Switch (MB Owners Manual page 365 for reference to page numbers, relevant/settings/operation.)
In addition to the above controls there is an air conditioning sensor located behind the Internal light fitting, which is sampling air all the time the ignition is on. This air is taken in through the intake port which can be seen on the right hand side of the the main lighting unit. Photos available on the section dealing with internal lighting where this unit can be seen.
The compressor of your A/C system is used to increase the refrigerant pressure in your A/C system in order to reach a "for our environment" suitable boiling point. Reaching this boiling point the gaseous refrigerant is condensed (condenser) to a liquid. Evaporating the liquid refrigerant (evaporator) it will absorb high quantities of heat, it will take from the air passing through the evaporator fin. Therefore the temperature of the Air is reduced and cooling the interior of your car.
Air Con Component parts in
are working at Low Pressure & Low Temperature. System parts in
are working at High pressure & High Temperature. Starting at the
which compresses the LP pressure vapour (Inlet) to a high pressure vapour (Outlet )the HP vapour is then passed to the
, some times known as the heat exchanger, In the case of the 'A' Class the condensed is situated directly in front of the radiator, as the cool atmospheric air currents pass through the condenser the heat absorbed from the the car and radiator is finally dispelled into the atmosphere.
Shows the radiator ,
shows the condenser At the condenser the high pressure vapour is condensed to a high pressure liquid, which is then passed to the
where it is filtered and dried. Clean dry high pressure liquid is then passed to the
where the high pressure liquid is changed to a low pressure mixture of liquid
and vapour, which is in turn passes to the Evaporator
where the refrigerant is again turned back to a pure low pressure vapour, which cools the inside of the car by absorbing the heat, having done its job it passes on back to the compressor where the cycle starts again .
Owners of cars with Air Conditioning are advised NOT to Tamper or attempt repair, discharge or recharge the system, but to use the services of a specialist Company.
Specialist equipment set out for servicing the Air Conditioning recommended every 2 years or 20000 miles This car is just over two years old and has done 22000. The Filter/Dryer B
(above) element is replaced every other service.
1 Cylinder for containing the used gas which is then disposed of in an environmentally safe way. 2
This cylinder contains new refrigerant gas R134a. which apparently has a less damaging effect on the ozone layer than
gases previously used, such as Freon (Carbontetrachoride) and in the case of earlier domestic fridges and freezers, Sulphur Dioxide. SO.
The Appliance used for reclaiming the old gas from the system
with hoses, connected to the expansion valve and valve located on the front of the Condenser. Both are fitted with Schrader type none return valves, protected by plastic caps.
The cylindrical unit pre-connected to the replacement Gas Cylinder, item 2
is the vessel into which the new oil for topping up the system is placed prior to being discharged along with the New Refrigerant into the Air Con circuit. 5
Gauge assembly which allows the service engineers to see the status of the H.P & L.P system during the discharging and recharging process.
Low pressure hose connected to the Expansion Valve.
Details of the type of refrigerant and lubrication are available on a label affixed to the n/s of the bulk head.
High pressure Hose connected to the Valve located on the front of the Condenser 8Condenser Its location makes it vulnerable if the vehicle is involved in a road accident. Where a fracture or leak is caused, whether on the highway by road accident or in the confines of a workshop due to mishap, every precaution should be taken to avoid breathing the vapour or direct contact with the skin, the gas given off by this refrigerantR134a (1,1,1,2-Tetrafluoroethane) is Asphyxiating, toxic, and flammable, direct contact with the skin can cause burns. The gas when in form is heavier than air. If working below the vehicle or in a confined space, evacuate immediately to open air. Although only 600 gram's of liquid refrigerant is installed in the system, when allowed to escape to atmospheric the gas will expand to form a small gas cloud, certainly sufficient to contaminate a workshop area, and the area around the car.
The gauges in the photo are showing the High and Low pressures that exist in the newly charged system. The refrigerant being measured by weight. 10
The Glass covered chamber between the two gauges enables the engineer to see the 2 fl.oz of New oil used to top up the systems lubrication which is carried into the system along with the new refrigerant. A fully serviced units lubrication would contain between 7 & 10 fl.oz dependent on the size of the system.
The Filter/Dryer which contains desiccant is responsible for Filtering and drying the refrigerant contained in the system. In the case of my recent service this was not changed , however it will be changed on the next service in two years or when the car reaches 40000 approx. Note if your car's system has gone a long period without being serviced you would be advised to notify the engineer when arranging the appointment, he can then ensure he has the appropriate replacement filter/dryer element for your car. Where there is a need to change the Filter/Dryer additional costs for the part are incurred. One item of equipment I did neglect to photograph was the small vacuum pump which was used to create a vacuum (negative pressure)in the system circuitry after degassing, thereby ensuring that any contamination and moisture had been totally eliminated before the recharging took place .
The Air conditioning compressor is situated below the battery compartment, Drivers side and is accessed from below the car, A light weight protective cover shields it from the bulk of road grime, But would not afford it mechanical protection from misplaced trolley jacks etc so great care should be taken to avoid damaging the hoses attached to the compressor which contain refrigerant under pressure. The Compressor on the 'A' Class is fitted in tandem with the Alternator, along with the water pump they are all powered from the poly 'v' belt.
The compressor is driven by a pulley wheel
which is engaged permanently with the poly 'V' Belt situated on the o/s of the engine. The compressor pulley wheel has an integral electro-magnetic clutch system
when the air conditioning is switched on the electro-magnet is energised and the compressor is the driven by the poly 'v' Belt. When the Air Con is turned off the electro-magnet is de-energised and the compressor ceases to operate.
This is also claimed to be an 'A' Class compressor so if replacing your unit ensure you acquire the right one.
Other circumstances where the air conditioning compressor may cease to operate are:-
* Engine stall prevention( RPM to low (Air-con will switch off)
* Acceleration cut off (Full throttle A/C will switch off + or - 10secs)
*Ambient temperature (selected setting on A/C controls) within the vehicle is reached
*Blower motor switch will turn off A/C when the blower motor is switched off
*Excessive refrigerant pressure OR * Too low refrigerant pressure will switch off air conditioning
The above are the most common automatic control features used on vehicle air conditioning systems
Air Conditioning Compressor Problems. Generally speaking the compressor of the air conditioning system causes few problems.
However in a number of cases the outer main bearing (Poly V belt side) pulley collapses causing a lot of noise and concern for the owner. Se3e this mail from Rene who suffered such a problem.
Readers I sure would like to read this mail I received from Rene, in Slovakia which is very informative and may be helpful to other DIY readers.
Thanks for your great web page, which is like good spirit in the dark...
I have MB A140 with AC since 1999, +/- 140000km. Many people commented on the noise coming from my engine bay engine, I was thought that it was usual on all 'A' Class. After checking we came to the conclusion that it was either the alternator or the Air conditioning compressor , It turned out to be the Air conditioning compressor!(part A 230 59
11)On inspection we discovered a broken bearing this was located in the front cover, unfortunately we did not have a camera handy. The bearing which is a NSK (Japan) type 35BD5222DUM18A. has an inside diameter is 35mm. outside diameter 52mm, and width is 22mm. Korean 'KOYO' can offer you same type of bearing DAC355222. the cost of the bearing to repair the compressor was 30 (Most recent price obtained Spain 69 20/6/12) far cheaper than either buying a new or re-conditioned compressor. I hope this information will help somebody. Kind regards
Rene Badura, Banska Bystrica, Slovakia Very useful information many thanks Rene.
When I received an e-mail from another owner in Romania with noise problems I suggested he check the outer bearing of the Air Compressor, this can be done without degassing.
His reply :- Quote:- Dear friend, I change it the ball bearing from the AC compressor and the noise is gone!!
Thank you again for your useful help.
I find it here in Romania the bearing for 14uro and the worker asked me for another 15 for the fitting 29 euro only. MB service station said I have to change the AC compressor for
it is not hard to see how massive savings can be made on the repairs to your car with just a bit of advise and encouragement. and remember none of these jobs are covered in the standard servicing of your car by Mercedes-Benz or any other Service dept for that matter.
13.4.2011 However when Peter a fellow owner had noise problems he was well away from his home country, and the garage wanted to change the compressor which he refused, 500 being mentioned, they did however fit a new shorter poly V belt which they obtained thus deleting the compressor from the drive belt system which deleted the noise and will allow peter to get the 1000 miles back to his own country where he can get the bearing replaced.
The replacement belt that did the job 1355mm, length rather than a standard (not air con A class belt which is 1290mm) so that point is worth bearing in mind, faced with the same trouble it may well get you out of trouble,
Thanks Peter for the information and have a safe trip home.
Further problems faced by Tom of Spain revealed the the bearing had disintegrated (see right) the noise was described as:-quote. Recently there is a"gurgling" rattling mechanical noise coming from the right hand side of the engine.
It is not affected by bumps on the road.
It happens intermittently, more so when the engine is fully warmed up, and is sometimes present when the engine is ticking over.
Remember the location of the noise may be deceiving so investigate thoroughly before committing to a repair.
In Toms case he was able to obtain another compressor rather than replace the bearing at , in his case 68, he did also provide these photographs which may help others.
A Shows the components removed to free of the pulley wheel which houses the bearing, where the bearing is still in one piece a puller may be required to remove the pulley wheel complete with bearing However in such circumstances I do not think you will get problems of noise.
The bearing is a double race bearing, in this case part of the ball race is still in position on the shaft of the compressor motor. This will be firmly fitted to the shaft and my need to cut or ground off before the new bearing can be fitted,
complete with pulley drive wheel . B shows the compressor body and the shaft on which part of the
double race bearing can be seen.
Compressor pulley wheel showing the recess into which the new bearing is housed.
The Company, National Aircon were used to service my car's Air conditioning They were £100 cheaper than the verbal quote obtained from my MB dealer, I had the convenience of the Company coming to me and the car was not out of action for the day as it would have been if I'd got it done by my MB dealer. The two members of staff were efficient , well presented and knew their job, as well as arriving in a 2001 MB veto. The complete job was done to my satisfaction in approx 45 minutes. I am pleased with the results, my Air Conditioning is far more effective , and having since used the car on one of the warmest days of the year. I am pleased I had it serviced. I would definitely recommend the services of
Whose telephone number I obtained from yellow pages.
This Photo has been included following a lot of interaction on the BB owners club site, http://baby-benz.com Re-gassing Air Con pages 1,2,3, jpg suggested that I include a photo showing the temperature reached with the air con on since re-gassing. Four shots are included in this photo, time taken and temperature are as seen and recorded by the inbuilt thermometer/clock, The temperature fell to 7c over a period of about 13 mins with the engine running at about 1500rpm. Agreed it wasn't a nice day and the sun was tucked up well behind thick clouds but the Air con certainly feels more effective that it was before being re-gassed, and as far as I'm concerned 'The proof of the pudding is in the eating' or in this freezing! In conclusion whether you have your Air Con system serviced is up to you! But if you are driving a car with Air con fitted and are not feeling the benefits when held up in traffic jams and alike you might as well not have fitted at all.
One of the commonest questions!
When I drive with my Air con operating and then stop my car water or fluid can be seen dripping, forming a puddle beneath the car?
This is normal. The air conditioning works like a refrigerator, ice will form on the external surfaces of the metal pipe work of the unit, this remains frozen, until the car is stopped at which time the ice thaws and thus water will be seen to puddle beneath the car. The amount of water deposited will depend on the atmospheric Humidity, Ken, in Honk-Kong for instance found that his car was depositing a lot of water, this is because Honk-Kong has a high humidity and therefore more ice is formed on the external pipe work. In fact its fare to say that if you do not see water beneath the car on a dry day, after having travelled some distance with the Air Con ON, that the system needs to be checked. But please remember the Air Conditioning is only ON (Working )When the light in the centre of the switch Marked
above which is the main air conditioning control, is
Remember also that the temperature control setting is what will determine whether the car is hotter or colder, along with the circulation fan which evenly distributes the selected air temperature. The mini fan/sensor in the interior light, which can on occasions be heard running or buzzing is sampling the air continuously all time the ignition is On When the engine is running the interior of the car will be kept at the drivers selected temperature if all is well.
With lights Air/heater/blower switches
Bulb failure, if your heater illumination fails on a 2001 onwards model then the dash has to be partially removed to replace the bulb
On pre February 2001 models Only (Pre face lift) On earlier models the centre heater dial/knob pulls off to expose the bulb.
This has to be removed using something like a BIC biro body and blu-tac or a piece of polythene Tube approx 5mm in dia,A Warm one end of the tube to make it supple and gently push it onto the head of the bulb, allow to cool and then withdraw. Because the bulb is recessed it will have to be replaced in the same way, using something like a drinking straw, insert this into the polythene tube genlty holding the bulb in it is housed position, ease the polythene tube from the bulb lens.
Bulbs are the same as used in the instrument cluster, See mypage 45 these are available from stores such as Halfords and cost approx £1.00 each.
Diagrams showing the settings below can be found in your owners handbook pages 119-127
However for those Owners who have not had the handbook passed onto them by the previous owner the following setting are displayed for the various conditions the white line on each of the dials being set as shown. In all cases adjust the controls to suit the occupants of the car. Talking over a fan that is permentally on full blast is annoying to say the least, as is being frozen to death by the owner who tries to impress you with the efficiency of the air conditioning. If the controls are used efficiently the modern vehicle can be a very comfortable environment for all passengers, allowing you to get away from the cold of winter and the heat of summer.
Do remember that some models do not have air conditioning, also the part the Activated carbon filter plays in air conditioning If you do get smells from the outside environment whilst driving turn off the Air - straight away.
Do remember that when the light displays on the button on the left the 'Air Recirculation' is ON
However when the light shows on the Air Conditioning (AC) button Air Conditioning is OFF
Basic Heater Settings Winter Set the controls as shown, Close the central air vents, Set the side air vents to half open, with the expelled air directed onto windows.
Maximum Heat output (Winter) Set the side air vents to half open The air flow directed onto the side windows.
Basic ventilation (Summer ) Turn the air flow as required, to at least position 1 (one) Open the centre and side vents as required
Misted up windows (Inside) Close the centre vents, Open the side vents and direct them at the side windows. Note that the 'Air Recuirculation' has been turned, ON This is indicated by illumination of the small light built into the button. To turn off 'Air Recirculation press the button again and the light will go out.
Windscreen misted up on the outside. Switch the Wipers ON Stopping them as soon as the moisture is cleared Running the wipers on a dry screen is likely to damage the rubber composite blades and cause unnecessary wear.
Special settings use for short periods only Only select for short periods /Defrosting Open the side air vents and direct them at the side Windows.