Apple began including liquid contact indicators (LCI) in its iPods and iPhones in 2007 and also added them to its MacBook and MacBook Pro computers in 2008.
The company uses these sensors to determine the eligibility of devices for repair under warranty.
Devices brought in for service that have been damaged by water or some other liquid are not covered by Apple's one-year limited warranty or the company's AppleCare Protection Plan.
The lawsuit filed last week alleges that Apple "uses [the LCIs'] false-positive readings to avoid its [warranty] obligations..."
The plaintiff in the case, San Francisco resident Charlene Gallion, had two iPhones cease functioning in the space of six months, neither of which, her complaint claims, had been damaged by any liquid.
Apple says that its LCIs "are designed not to be triggered by humidity and temperature changes that are within the product's environmental requirements described by Apple."
Gallion's claim essentially disputes this.
The complaint says that Gallion brought an iPhone in to an Apple store for repair and was denied warranty coverage because the Apple representative determined the device had been damaged by liquid.
Gallion insisted that her iPhone had not been damaged by exposure to liquid, but had no way to challenge the determination of water damage made by Apple's representative. She was allowed to purchase a new iPhone at a discount, provided that she paid the tax on the full price and traded in her non-functional iPhone.
Six months later, her new iPhone stopped working. Again, an Apple store representative denied her warranty coverage because the liquid contact indicators showed that the phone had sustained water damage.
Gallion knew her phone had not been damaged by liquid, according to the complaint, but believed it would be futile to argue the point.
As a consequence of such policies and misrepresentations about the accuracy of its liquid sensors, the complaint says, "the right to coverage under the Standard Warranty and the Extended Warranty is rendered illusory."
The complaint states, "As a result of Apple's improper application of the Liquid-Damage Exclusion, Apple sells [devices] with the intent to exclude them from the warranty coverage Apple promises consumers it will provide -- even when consumers pay extra for Extended Warranty coverage -- simply because their Liquid Submersion Indicator has been triggered, without any attempt by Apple to verify whether the Class Devices actually have been damaged as a result of submersion or immersion in liquid."
An Apple spokesperson was not immediately available for comment.