The difference between accumulators and receivers is that the former belongs in the low pressure part of the A/C system and the latter belongs in the high pressure part. They both act as containers for the liquid refrigerant that should not pass through to the compressor; only the vapour should be allowed to escape from either. When the filter in the receiver drier fails, moisture gets through to the compressor and causes corrosion. This can occur when unwanted liquids and debris get into the system during manufacturing, or even when your car is subjected to extended periods of high humidity. It does not take long before such corrosion prevents your A/C system from working altogether, so be sure to get your accumulators and receiver driers double-checked during every service – they often get overlooked.