If the only reason you're asking the umpire to check with his partner is that it was a close play, you didn't like the outcome, and you're fishing for a second opinion, then the umpire shouldn't check with his partner.
If that sounds a little too harsh, let me explain. If an umpire is in position for the play, sees the elements he needs to see- the base, the ball, the runner, and the fielder- then it's his call to make. That's the job he's being paid to do! If he saw what he was supposed to see and is sure of what he saw, then there's not really any reason to get a second opinion. Sure, you can ask him to get help, but he's under no obligation to do so.
On the other hand, suppose there was something he didn't see. Sometimes you can get caught out of position and not get the best look at the play. Sometimes players block your view. Sometimes a throw is off line and there's a swipe tag that's on the opposite side of the player from where you were set up. Sometimes fielders pull their foot off the base and if they're pulled straight at you their foot is hidden. Sometimes a fielder loses the ball on a tag and the umpire misses it.
If any of those happen, any of which is beyond the scope of a routine play, then by all means you should ask. And if the umpire knows he might of missed something, then by all means he should consult with his partner. But again, he's under no obligation to. If you know you missed something, to me it be becomes a question of integrity. You should try to get it right.
Even if he does get with his partner, he's not under any obligation to change his call. And it's always possible that his partner doesn't have any info that will help, if he had other runners to watch on the play. At least you're exhausting every avenue you have to try and get the call reversed.
The two biggest problems I see with getting help is that some umpires are just too hard-headed to admit they missed something and refuse to get help, and some coaches think that they should get help on every close play that doesn't go their way. The reality is somewhere in the middle. There are times when an umpire definitely should get help, and there are times when he definitely shouldn't.