The iPhone is one of the most successful gadgets ever. Last week it helped Apple overtake Microsoft as the world's biggest technology company but as sales grow so do complaints.
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Owners whose phones have developed problems have been accused of damaging them and the company has refused to pay for repairs.
But Watchdog has looked into some of these cases again and it might be time that Apple did too.
iPhones have touch screens, GPS, the internet and much more but some of the more sophisticated features are the ones you can't see including a bit of technology that's causing some of you grief...
It's called a 'liquid contact indicator'. Normally they're found on the inside of phones but the iPhone has two of them you can see from the outside, one in the headphone jack and one in the charger port.
They work a little bit like litmus paper. When water touches them, they turn red and that helps manufacturers work out whether your phone's been damaged by water.
But some viewers such as Shaun Kelly have told us that isn't always the case:
"I know for fact that my iPhone hadn't been near water, but when I went to the Apple shop they just said it's been immersed in water and as such you have to buy a new phone Mr. Kelly. And it's tough luck."
Mike Hughes was another:
"My iPhone has had the occasional rain drop on the screen. It's not been dropped in a cup of water, its not been dropped in a puddle and I couldn't see how there was any way it was water damage."
The Apple user guide states that if your phone has been damaged by water then it's not serviceable. This means you can't get a repair without paying and your warranty is void.
But the big question is - just because the indicators on the outside turn red does that mean your phone has actually been damaged by water? And does Apple bother to check?
Aatif Raifiq's phone developed problems in April - the WiFi and Bluetooth both stopped working. Apple's Manchester store told him he had one red tab at the bottom of his phone, the result, they said, of water damage.
Aatif couldn't see how that could be the case:
"It's never been close to any water - you wouldn't take it swimming with you or into the shower - you wouldn't do any of that."
It was the same story when he called Apple customer service. They were adamant that if the tab had turned red there was evidence of liquid damage and therefore his warranty was void.
To find out for sure whether Aatif's iPhone had been damaged by water Watchdog showed it to some high-tech engineers to investigate further.
Before they opened Aatif's phone they could see there was a red tab on the outside. However, when they opened the phone up, there was no damage to the mainboard whatsoever. In fact, they told us that it looked like nobody had opened his phone before them to check.
The question they raised was how without Apple actually opening it, can they prove that there's liquid damage to the device?
The engineers found that Aatif's internal indicators were clearly white - a sure sign there was no water damage inside.
So is Apple being thorough enough with their own checks?
And what is turning these outside indicators red? Are they too sensitive? Some customers in the US think they are as they've just filed a lawsuit against Apple.
They say the company has blamed tiny amounts of moisture, even sweat, for turning the tabs red.
So how much water does it take to actually trip one of these sensors? We made a number of calls to Apple, posing as a customer with one red sensor. They listed several reasons why sensors could be triggered without actually dropping the phone in a puddle or down the loo.
These included having it near a shower or using it in the rain which are both mentioned in the manual. However, we were also told to not have it in a moist area like a wet hand and that the problem could be due to condensation.
So if a mere drop of rain, condensation or sweat can make your outside indicators go red, how many iPhone owners are walking around with voided warranties and not realising? We checked fifteen iPhones at random on a busy shopping street and found that three of them had red tabs and their owners had no idea.
It is worth remembering that if you open your iPhone at home you will void the warranty.
Apple told Watchdog the following:
"If an iPhone has been damaged by liquid, the service or replacement is not covered by the Apple one year limited warranty or an AppleCare Protection Plan (APP). It would be eligible for Out Of Warranty Service. Currently, if a customer takes their iPhone to an Apple Retail Store, the warranty will only be void due to liquid damage if all indicators have been triggered.
Further information on iPhone warranty can be found on Apple's website:
http://www.apple.com/uk/support/iphone/service/exchange/
Please note: The BBC is not responsible for the content of external sites
Watchdog bites Apple...
In order to see this content you need to have both Javascript enabled and Flash installed. Visit BBC Webwise for full instructions. If you're reading via RSS, you'll need to visit the blog to access this content.
Owners whose phones have developed problems have been accused of damaging them and the company has refused to pay for repairs.
But Watchdog has looked into some of these cases again and it might be time that Apple did too.
iPhones have touch screens, GPS, the internet and much more but some of the more sophisticated features are the ones you can't see including a bit of technology that's causing some of you grief...
It's called a 'liquid contact indicator'. Normally they're found on the inside of phones but the iPhone has two of them you can see from the outside, one in the headphone jack and one in the charger port.
They work a little bit like litmus paper. When water touches them, they turn red and that helps manufacturers work out whether your phone's been damaged by water.
But some viewers such as Shaun Kelly have told us that isn't always the case:
"I know for fact that my iPhone hadn't been near water, but when I went to the Apple shop they just said it's been immersed in water and as such you have to buy a new phone Mr. Kelly. And it's tough luck."
Mike Hughes was another:
"My iPhone has had the occasional rain drop on the screen. It's not been dropped in a cup of water, its not been dropped in a puddle and I couldn't see how there was any way it was water damage."
The Apple user guide states that if your phone has been damaged by water then it's not serviceable. This means you can't get a repair without paying and your warranty is void.
But the big question is - just because the indicators on the outside turn red does that mean your phone has actually been damaged by water? And does Apple bother to check?
Aatif Raifiq's phone developed problems in April - the WiFi and Bluetooth both stopped working. Apple's Manchester store told him he had one red tab at the bottom of his phone, the result, they said, of water damage.
Aatif couldn't see how that could be the case:
"It's never been close to any water - you wouldn't take it swimming with you or into the shower - you wouldn't do any of that."
It was the same story when he called Apple customer service. They were adamant that if the tab had turned red there was evidence of liquid damage and therefore his warranty was void.
To find out for sure whether Aatif's iPhone had been damaged by water Watchdog showed it to some high-tech engineers to investigate further.
Before they opened Aatif's phone they could see there was a red tab on the outside. However, when they opened the phone up, there was no damage to the mainboard whatsoever. In fact, they told us that it looked like nobody had opened his phone before them to check.
The question they raised was how without Apple actually opening it, can they prove that there's liquid damage to the device?
The engineers found that Aatif's internal indicators were clearly white - a sure sign there was no water damage inside.
So is Apple being thorough enough with their own checks?
And what is turning these outside indicators red? Are they too sensitive? Some customers in the US think they are as they've just filed a lawsuit against Apple.
They say the company has blamed tiny amounts of moisture, even sweat, for turning the tabs red.
So how much water does it take to actually trip one of these sensors? We made a number of calls to Apple, posing as a customer with one red sensor. They listed several reasons why sensors could be triggered without actually dropping the phone in a puddle or down the loo.
These included having it near a shower or using it in the rain which are both mentioned in the manual. However, we were also told to not have it in a moist area like a wet hand and that the problem could be due to condensation.
So if a mere drop of rain, condensation or sweat can make your outside indicators go red, how many iPhone owners are walking around with voided warranties and not realising? We checked fifteen iPhones at random on a busy shopping street and found that three of them had red tabs and their owners had no idea.
It is worth remembering that if you open your iPhone at home you will void the warranty.
Apple told Watchdog the following:
"If an iPhone has been damaged by liquid, the service or replacement is not covered by the Apple one year limited warranty or an AppleCare Protection Plan (APP). It would be eligible for Out Of Warranty Service. Currently, if a customer takes their iPhone to an Apple Retail Store, the warranty will only be void due to liquid damage if all indicators have been triggered.
Further information on iPhone warranty can be found on Apple's website:
http://www.apple.com/uk/support/iphone/service/exchange/
Please note: The BBC is not responsible for the content of external sites
Watchdog bites Apple...