Accumulator — What is an AC accumulator

What is an AC accumulator?

An AC accumulator is used to collect and store any liquid refrigerant that may flow out of the evaporator coil. Since liquids cannot be compressed, it’s critical that only refrigerant gas enters the AC compressor. The accumulator allows only a regulated amount of refrigerant oil and refrigerant gas to enter the AC compressor.

As liquid refrigerant and oil enter the accumulator inlet, they hit a baffle near the top that distributes the oil and liquid to the sides of the accumulator, where it falls to the bottom. A U-shaped tube is attached to the outlet of the accumulator. The inlet to the U-shaped tube is located near the top of the accumulator so it can’t suck any liquid refrigerant into the compressor. The tube contains an oil suction hole at the base. At the bottom of the accumulator, the liquid refrigerant contacts a bag of desiccant. The desiccant absorbs and stores any moisture that would contaminate the refrigerant. This moisture alters the chemical structure of the refrigerant and may freeze, corrode, or damage vital system components. When it’s saturated with moisture, the entire accumulator must be replaced. See the image below.

Where is the AC accumulator located?

The AC accumulator is located on the outlet tube of the evaporator coil, usually in the engine compartment and near the firewall.

AC accumulator in engine compartment near the firewall

The accumulator takes advantage of the engine compartment heat to boil the liquid refrigerant and turn it back into a gas so it can be compressed by the compressor.

Which AC systems use an accumulator?

Accumulators are only used on orifice tube style automotive AC systems. Orifice tube systems often don’t fully convert liquid refrigerant to a gas, which means liquid refrigerant could leave the evaporator and flow into the compressor, destroying it.

Why does the shop want to replace my accumulator?

There are no moving parts in an AC accumulator. But once an automotive AC system fails, debris and moisture can deposit in the accumulator. Also, if the AC system is open to the atmosphere due to a broken hose or leaking evaporator or condenser, the desiccant bag in the accumulator can soak up too much moisture, rendering it useless. Most compressor manufacturers’ warranty terms require the installation of a new accumulator any time the compressor is replaced. Failure to replace the accumulator can void your compressor warranty.

©, 2018 Rick Muscoplat