Mercedes-Benz R107 Air Conditioner Compressor Replacement | 1972-1986 - 450SL, 380SL, 500SL, 560SL (2024)

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. In a nutshell, the air conditioner works by a system of 4 processes: Evaporation, Condensation, Compression, and Expansion.

Here is how the 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 R-134A moves to the receiver, which is a small reservoir. This removes any moisture 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.

The whole process is really pretty cool (had to say it).

The air conditioning compressor does the bull work and is located on the driver side within the engine compartment behind the radiator. It is driven by a belt and is next to the water pump. Over time, the compressor unit may fail. The unit itself is not cheap to replace, so before you buy a new one, pressure test the system first and verify the location of any leaks. If there is a hole in the system that allows it to run dry, even though the compressor has its own internal oiling system, there will be a chance you will need to replace the compressor as well. If there is a hole in the system, we do NOT recommend using products that will fix leaks by injecting a product into the AC system (much like fixing a flat tire). These products can cause serious problems with your AC system and should you use them, most garages will refuse to work on your AC system should you need professional repairs later. In this article I will show you how to replace the compressor.

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 articles on drive belt, shroud and radiator removal for further assistance. For additional information on the AC system, please see our articles on: Replacing the AC Evaporator and Replacing the AC Receiver/Drier Accumulator and Replacing the AC Belt.