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Replacing the Air Conditioner Receiver Drier
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Pelican Technical Article:

Replacing the Air Conditioner Receiver Drier

Mike Holloway


30 minutes30 mins


$23 to $185




13mm socket wrench, 13mm open ended wrench, 12-inch extension, universal socket

Applicable Models:

Mercedes-Benz R107 (1972-89)

Parts Required:

AC receiver drier, may also require sensors

Hot Tip:

Remove any component to provide more room

Performance Gain:

A properly cooled car

Complementary Modification:

Replace the existing refrigerant with R-134A

Before you do any work on your car it is important that you wear safety glasses, work gloves and dispose of all fluids in a safe manner. Coolant is poisonous and should be treated as such. Animals and small children have been known to die from ingesting coolant. If you have to jack up your car, make sure to use jack stands and chock your wheels as well as applying the parking brake. Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability. Always wear eye and hand protection and disconnect the battery.

The air conditioner not only cools the airflow but it also reduces the humidity. The air conditioner works by a system of 4 processes: Evaporation, Condensation, Compression, and Expansion.

So here is how the whole process works in your car:

Step 1) The AC gets turned on.

Step 2) The compressor pumps the refrigerant (R-134A) to the condenser. The R-134A is under high pressure. A belt driven by the crankshaft powers the compressor.

Step 3) The condenser converts the gas into liquid because of the high pressures. This also generates heat during the process. The condenser looks like a radiator and actually acts like one. The circulation and the fins of the condenser help cool the R-134A.

Step 4) The liquefied R0134A moves to the receiver/drier accumulator, which is a small reservoir. This removes any water that may have leaked in. When there is moisture present it can form ice that reduces flow or worse, it can create damage to the compressor.

Step 5) After the liquefied R-134A leaves the receiver, it goes through an expansion valve. This valve opens up the volume for the liquefied R-134A to become gaseous.

Step 6) The gaseous R-134A is pumped to the evaporator. The evaporator looks very similar to the condenser or the radiator. The evaporator is where the real cooling takes place. As the cold, low pressure R-134A flows into the evaporator, it vaporizes even more so and pulls heat from the air circulating throughout the cabin. A fan pushes air over the fins of the evaporator so that cold air is circulated throughout the car.

Step 7) The process continues because the R-134A flows back to the compressor to start the refrigeration cycle all over again. The expansion valve regulates the degree of chilliness.

A word of note before you start: The AC system is charged with a refrigerant that is both dangerous and illegal to discharge into the atmosphere. If you are going to be working on the system make sure you have the refrigerant properly evacuated and reused or disposed of. Discharging, evacuating, and charging the AC system must be performed by properly trained and certified technicians. In a facility that has a recovery and recycling system that adheres to the SAE standards.

There are a couple important facts about the refrigerant that you should be aware of. First it is really cold. If it contacts your skin it will give you severe ice burns. Another consideration is that if the refrigerant comes in contact with an open flame it becomes very toxic and even a small whiff can be fatal. Do not apply any heat to the system of any hardware located near the AC system. It is best to check and see if there is any refrigerant in the system. This will be the first thing covered. You will need to remove the drive belt, shroud and radiator before beginning this job. Please see our article on drive belt, shroud and radiator removal for further assistance.

The air conditioning receiver drier removes any moisture that may accumulate over time. Moisture can contribute significant damage to the various components in the AC system. Receiver/driers (AKA "filter/driers" or "receiver/dehydrators") are small reservoirs with an inlet and outlet located on the evaporator--which looks like a small radiator mounted in front of the radiator.

The receiver/dryer accumulator has several functions. They act as a temporary storage container for oil and refrigerant during periods of low cooling demand. This is the "receiver" function of the receiver/drier. They contain a filter material that captures wear materials or contaminates that may circulate through the system. It also contains a drying desiccant material designed to absorb moisture that may have gotten inside the A/C system during manufacture, assembly or service.

Damage can occur if there's excessive moisture inside an A/C system. It can cause corrosion, as well as possibly degrade the performance of the compressor's lubricating oil. The receiver/drier should be replaced any time the system is opened for service, and most compressor warranties require it. The desiccant is only capable of absorbing a certain amount of moisture, and when the inside of the system and/or the receiver/drier are exposed to the atmosphere, the desiccant can become very quickly saturated from humidity in the air. If this occurs, the desiccant is no longer effective. The filter may become restricted diminishing refrigerant and oil flow.

Receiver driers rarely fail themselves, but as mentioned previously, need to be replaced whenever the system is opened for any other type of service. When a failure does occur with a receiver drier, it is usually due either to clogging from debris inside the A/C system (like from a failing or failed compressor), or the bag containing the desiccant has broken open, allowing desiccant material to circulate throughout the system with refrigerant and lubricant. Sometimes, the desiccant material will disintegrate into small sand-like particles. This can cause possible clogging in other system components.

For additional information on the AC system, please see our articles on: Replacing the AC Compressor and Replacing the AC Evaporator and Replacing the AC Belt.

The receiver drier is replaced as follows. You will have to remove the grille as well as the cross-section bars that hold the axillary AC fan in place. Please refer to the articles on grille and auxiliary fan removal.

Before you start to take off the receiver drier, check the system for refrigerant.
Figure 1

Before you start to take off the receiver drier, check the system for refrigerant. This is done by pressing in the Schrader valve and seeing if any refrigerant comes out. There are two Schrader valves on the AC lines. These valves are almost identical to the valves used on tires. Using a flathead screwdriver, depress the valve to see if the system has been evacuated. The refrigerant is going to be very cold so make sure you are wearing gloves and eye protection. Just depress the Schrader valve quickly to see if there is any refrigerant in the system. If there is, always make sure you have the refrigerant properly and professionally evacuated. Most places will give you a credit or store your refrigerant until you can place it back in the system later. They may also charge a disposal fee. You will have to have them charge the empty system.

The receiver dryer is found behind the grille on the driver's side.
Figure 2

The receiver dryer is found behind the grille on the driver's side. The grille and cross members for the auxiliary fan will have to be removed.

Disconnect one lead to the receiver drier.
Figure 3

Disconnect one lead to the receiver drier.

Disconnect the other lead.
Figure 4

Disconnect the other lead. These can be moved out of the way in order to get at the couplings.

Using a 22mm open end wrench or 22mm crows-foot wrench and an adjustable open ended wrench, loosen the coupling on the receiver drier.
Figure 5

Using a 22mm open end wrench or 22mm crows-foot wrench and an adjustable open ended wrench, loosen the coupling on the receiver drier.

Repeat the same process on the opposite side of the receiver drier.
Figure 6

Repeat the same process on the opposite side of the receiver drier.

Using a 10mm wrench, loosen and remove the bolt holding the receiver drier in place.
Figure 7

Using a 10mm wrench, loosen and remove the bolt holding the receiver drier in place.

The receiver drier is now free to be replaced.
Figure 8

The receiver drier is now free to be replaced. Installation is the reverse of removal.

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