Mercedes Benz A/C System

Mercedes Benz has always been associated with rich and famous. They are popular for incorporating finest engineering and craftsmanship. Thus, results in high manufacturing costs. Air conditioning system equipped in Mercedes Benz is one of the major factors for comfortable and pleasurable ride. There are five major components that plays key role in the effective performance of the Mercedes Benz AC system. They are Mercedes Benz compressor, Mercedes Benz refrigerant, Mercedes Benz condenser, Mercedes Benz expansion valve and Mercedes Benz drier or evaporator.

During air conditioning process, refrigerant is placed under pressure by the compressor and sent to condensing coils. These coils are usually present in front of radiator. After compression, gas heats up a lot. Later, gas condenses into liquid and this change turn it hotter. Now, lots of heat is lost by refrigerant followed by sending liquid to evaporator.

On the high side of AC system, Mercedes Benz receiver drier or Accumulator is used. A thermal expansion valve is used by the Mercedes Benz receiver-drier. Liquid refrigerant is required by such metering valve. In order to ensure that valve is getting liquid refrigerant a receiver is also used. Separation of gas and liquid is the major function of receiver-drier.

Mercedes Benz AC receiver-drier also eliminates moisture and filters out dirt. A sight glass is also mounted on the top of Mercedes Benz AC receiver-drier or accumulator. Sight glass usually charges system. If the air conditioning system is working appropriately then vapor bubbles will not be visible in sight glass.

When the system is empty, it would be advisable to change Mercedes Benz receiver-drier or accumulator. You must change it after three years as desiccant pellets break down. Thus, results in clogging of expansion valve. This will make the system inoperable and compressor will be damaged.

A regular check up is essential for the adequate working of Mercedes Benz AC system. If any of the Mercedes Benz AC components is not worn out then repair or replace it immediately. High quality Mercedes Benz AC parts are available at autopartsfair.com. Autopartsfair.com offer huge range of high quality parts in varied range and styles. You may browse through the extensive range of parts available at autopartsfair.com. These high quality Mercedes Benz AC parts are available at discounted prices. Mercedes Benz AC parts available at autopartsfair.com are reliable and durable, as they have met original manufacturer specification. Autopartsfair.com also offers significant installation and maintenance tips for Mercedes Benz AC parts. Just log onto auatopartsfair.com and order the required part now.

Mercedes M-Class Model 163 climate control system '98 to '01

The heating, ventilation, and A/C (HVAC) system in the M-Class has semiautomatic temperature regulation and manual control over the air source and distribution. The temperature control is achieved without the use of a heater valve, also called mono valve in other models. The M-Class heater core is thus always hot, at about 87 deg C.

Air Conditioning Switch

The On/Off switch connects to the A/C control module (N19), which, through the All Activity Module (N10) controls the activation of the air conditioning compressor clutch. The A/C compressor operates only when the engine is running and the blower motor is switched on. The AAM (N10) also uses other information from the CAN to choose when to operate the compressor clutch, i.e. engine temperature.

Air Temperature Control

An NTC resistor behind a grille below the low range switch senses the in-cabin temperature. A hose connects it to the main climate box thus drawing air across the sensor.

Air temperature is controlled by a variable resistor rotary control. Signals from the resistor to the amplifier determine the desired interior temperature output of the system. A switch at detent position at the full counter clockwise (maximum cooling) position overrides the air recirculation switch to close the fresh air door for maximum interior cooling (with A/C on).

Air Distribution Control

The switch contains 12 detents for air distribution. A cable operates air distribution doors to direct air flow in the air distribution system to the air flow outlets. The air flow outlets are:

• Front windshield defroster/side window.

• Face outlets.

• Foot outlets.

Air flow from the above outlets depends on the position of this switch and the center air outlet control wheel above the temperature control panel.

Blower Motor Switch

Off and 4 blower motor speeds are available. Switch must be in position 1-2-3 or 4 for temperature system to provide either heated or cooled air. The switch is an input to the amplifier (N19). The logic circuit in the amplifier directs system voltage to the relay/blower motor resistor (R14) for reduced blower speeds (positions 1-2-3). The switch bypasses the resistor for the highest blower speed (position 4).

Fresh/Recirculation (FRS/REC) Switch

The switch selects the air to circulate either interior air or fresh outside air. The On/Off switch controls the air door motor which is linked to the door.

Air Conditioning/Heating Control Module (N19)

The A/C Amplifier (N19) is the control unit for the heating and air conditioning system. The A/C control module senses input signals from the various components and then determines if conditions are met for proper operation. The A/C control module then outputs control signals to energize various actuators directly or signals the AAM (N10).

The A/C control module receives input information from the following devices:

• Air conditioning switch.

• Interior air temperature sensor (NTC resistor below low range switch).

• Temperature selector control.

• Blower switch control.

• Evaporator temperature sensor.

• Air mixture flap door position signal.

The A/C Control Module sends control signals to the following devices:

• Air mix damper door motor.

• AAM (N10).

• Fresh/Recirculation (FRS/REC) door motor.

All Activity Module (AAM) (N10)

The AAM determines if certain conditions are met for the air conditioning/heating operation.

It receives input from the following devices:

• Hi-Low pressure sensor (via CAN).

• Engine coolant temperature sensor (via CAN).

Sends control signals to the following devices:

• Air conditioning compressor clutch.

• Condensor fans via relay.

• Relay K21 to power the blower motor.

A/C Compressor

The Denso A/C compressor is a 7 cylinder variable pitch swash plate design similar to the model 210 (E-Class). It is driven by a serpentine belt from the engine crankshaft and activated by an electric clutch controlled by the AAM. If it doesn't come on it might be a bad/lose connection on the underside of the fuse box sometimes at connector M/A pin 2.

Air Mix Damper Door

The mechanical door is controlled by a linkage from the servo electric motor. The door covers/uncovers the air passage through the heater core to mix heated and cool air in correct proportion needed to achieve desired interior temperature. A feed back potentiometer sends a signal to N19 (controller) for door position.

System Operation

Air Flow

Outside or interior air for the HVAC system depends on the position of the FRS/REC (air recirculation) switch.

The blower motor provides air flow through the system. If the blower switch is OFF, there is no air flow through the system. With the switch ON, air flows from the blower motor into an air filter before passing through the evaporator fins into the air distribution housing.

A moveable air mix damper door directs air around and/or through the heater core on its way to the air distribution ducts.

The quantity and proportion of air through each air distribution duct depends on the settings of the air distribution switch on the control panel.

Air Temperature, Cool

If maximum cool air is needed (A/C ON), the air mix damper door directs all cold air around, not through, the heater core.

The air temperature sensor provides a reference temperature midpoint setting of 68 deg F. During system operation, the temperature switch setting, relative to this reference point, will cause the air mix damper door to move and regulate the air temperature accordingly.

When the temperature control is set for maximum cooling, the outside door closes in order to increase the performance of the system.

Air Temperature, Hot

When the A/C switch is OFF and maximum hot air is needed, the air mixture damper door directs all air through the heater core.

Air Temperature, Warm

When warm air is needed, the air mix damper door moves to direct air around and through the heater core to arrive at the desired air temperature setting.

A/C System for Sprinter and Crafter

Behr, a specialist for car and truck air conditioning and engine cooling systems, and Behr Hella Thermocontrol,(BHTC), the Behr-Hella joint venture specializing in climate control, in collaboration with DaimlerChrysler, have developed the air conditioning system for the new Mercedes-Benz Sprinter and the VW Crafter. Birgit Kelm, head of Truck Customer Projects at Behr, emphasizes the company’s level of involvement: "We not only took responsibility for implementing the air conditioning system itself, but also provided customer support in our role as consultant and systems integrator. We combined all the HVAC components into a single system, irrespective of whether the components came from us or from another manufacturer.”

The Mercedes-Benz Sprinter and the VW Crafter, developed in a joint project by DaimlerChrysler and VW, both have a standard heating system and the optional "Tempmatik” air conditioning system. When the temperature is adjusted manually, Tempmatik automatically factors in the temperatures of the vehicle cabin, outside air, evaporator, and coolant, and uses this data to compute the ideal comfort climate. The blower speeds, too, are controlled as a function of the outside temperature, the vehicle speed, and the roof height of the interior. The control head for the heating and air conditioning system can be supplied in a total of 18 variants.

"The front seat air conditioning with the control head forms the control center for the HVAC system and is housed in the center section of the cockpit. ” continues Birgit Kelm.

"In the Sprinter, this air conditioning system can be supplemented with two alternative roof-mounted cooling systems if the vehicle is to be used for passenger transport. That way, passengers in the second and third seated rows also enjoy a high level of climate comfort.”

The heating and air conditioning system can be individually tailored to the application location and the intended use, since different air conditioning is required in hot countries compared with that in countries with temperate climates. It is also important whether the vehicle is to be used as a delivery van or for passenger transport. If the Sprinter is used for passenger transport, the auxiliary cooling system is suitable in temperate climates. This simply consists of an additional evaporator, and is integrated into the basic refrigerant circuit (this roof-mounted cooling system is also available for the Crafter). If the Sprinter is used in regions with extreme climate conditions, the more powerful system with a separate refrigerant circuit is recommended. Behr has designed both roof-mounted cooling systems in such a way that they fit into the gap in the roof intended for the sliding roof. This represents an advantage over standard roof-mounted climate control modules, which are normally housed on the roof at the rear, since, in addition to the more compact construction, the lines for the refrigerant are shorter and easier to integrate.

Mercedes Benz Air Conditioning Compressor

First of all, some compressors just wear out. You put a bazillion miles on them and their time is just simply up. However, the majority of the time the compressor fails is from lack of proper maintenance or the result of poor service procedures.

Let's remember that most of the A/C compressors that Mercedes Benz have used do not carry their own on board oil supply. The refrigerant oil is delivered throughout the system via the refrigerant.

Just as you would not run your engine without oil people attempt to run the air conditioning compressors without oil. How does this happen? Underneath the hood of your car is a pretty hostile environment subject to all kind of heat, cold, and vibration. Over time refrigerant may be lost through the various seals and out the front of the compressor. Since the refrigerant carries the oil it stands to reason that when you lose refrigerant you lose the oil at the same time. If you fail to replace the oil when you add new refrigerant you might as well log on and start pricing a new compressor. If you are not doing the job yourself, do not assume that refrigerant oil has been added. You must ask and make sure. It will be cold when you pick it up but not for long.
Preventive maintenance goes a long way. When you open the hood do a visual inspection of your Mercedes air conditioning system. Check your air conditioning hoses, Mercedes compressor, and Mercedes condenser for signs of leaks, that is oil residue at any of the joints or on the parts. Failure to repair the problem may damage or destroy the compressor since you are losing the oil that lubricates the moving parts of the air conditioning system.
If your Mercedes air conditioner is not working properly do not use it until you can check it out. This may prevent further damage. Remember that your compressor turns on when you turn on the defroster too so do not assume that it can wait till spring to have it repaired.