How to: Remove duplicate iPhone Address Book entries

I’m not a real iPhone doctor, but I play one on the Internet even though I don’t actually own one. Troubleshooting them for my friends and relatives isn’t particularly glamorous but it’s another way to vicariously enjoy the iPhone, furtive trips to the shops aside, in this AT&T provincial 3G backwater.

A friend of mine from afar wrote in with the following, seeking what assistance the intertubes might have to offer:

I bought a iPhone 3Gs yesterday. Everything seems to work great. The only exception is that my contact list on my phone has everything duplicated. At least two entries of all my contacts. I tried to find some ways to fix it last night but ran out of time. Do you know of any (quick) way to fix this?

I didn’t, but now I do.

Rob G at Mac OS X Hints explains that a new feature in iPhone OS 3.x.x could cause users who have been syncing their handheld to both MobileMe and their Mac (iTunes) to end up with two complete sets of entries — i.e. one for the Mac and a second for MobileMe. The problem is that iPhone OS 3.x.x now allows a user to sync both accounts at the same time, hence the second group of Calendar and Address Book entries.

Here, the trick is to disable Mac to iPhone syncing and leave MobileMe active (your Mac needs to sync there, too), which nips the original problem in the bud. So, with your iPhone tethered to your Mac, iTunes running and your device highlighted, go to Info and deselect any and all syncable items.

However, you’ll still be stuck with two groups (sets) of contacts, etc on your iPhone—here’s how to get rid of them:

On your iPhone or touch:

• Choose Settings >Mail, Contacts, Calendars, then tap your account, and slide to Off.
• When prompted, select Delete from My iPhone/iPod touch.

Now you need to re-enable syncing:
• Choose Settings > Mail, Contacts, Calendars, then tap your account to slide the data type on.
• When prompted, select Merge with MobileMe

See also: Knowledge Base Article HT3677, a.k.a. iPhone/iPod touch: Resolving duplicates and removing all contacts/calendars/bookmarks with MobileMe

This problem reproduces on my iPod touch running iPhone OS 3.1.2 and can be remedied by using the above method.

Got a neat trick you’d like to share? A problem without an answer? Pop us a note and link in the comments below…

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3. iPhone OS 3.1: MobileMe services get tweaked, too
4. iPhone OS 3.1[.1]: What’s inside this major update
5. How do I transfer songs from iTunes to iPhone?