Also here is a video guide
Original guide by Our Afflictions
It may be important to note, you must apply the backpack upgrades manually to unlock this.
He is hard to miss, fighting your way through the safe house, he is in the North West part of the map, right near some rubble, and close to a stairwell, listen for his moaning.
His repair kit is above you, when you are standing on the waypoint.
The Claptrap in the lost cave is at the point where there is a T intersection where the bandit outpost area is. (looking at the outpost as you enter) Where one path (left) leads to a dead end and the other path (right) leads to the spiral area.
The repair box is up the hill (following the rail tracks up and around) and just behind the second or third building in some pipes.
In town, right next to the bounty board. Self explanatory.
Crazy Earl's Scrapyard
When you enter the zone, take your left at the T (the maps right)
Fight your way through bandits and you will see him amongst the camps.
The repair kit is easy as well, just jump on the washing machine to get onto the platform, kill the bandits, and grab the kit.
When you enter the zone, go right. Let the game lead you to it from there on, if you really can't find him, he is (from the perspective of the right side of the map being the only part of the map for this discussion) at the North West part of that Canyon.
His kit is a few jumps away, just keep following the path.
North of where you started, before you get to the fork in the road, on the left side. The repair kit is farther north, staying left, above some metal structures in the first corner, farthest North West.
When you first enter, turn right and look at your map, you will see a fork in the road, go left then make your first right, the claptrap is in the middle of a bandit encampment right next to where a bunch of lava crab worms are.
If you find the shack on the ocean, its stright west of that and a little south.
Almost right in the middle of the SOUTHERN potion of the map..
The repair kit is on top of the pipe where the diamond leads. Follow it back to the trash pile, climb onto the pipe, and retrieve it.
He doesn't spawn, until you have completed the quest to save the claptrap from the cage. Once you have that quest enter the zone, and take the first right, and follow that street, as if you were heading towards the base of troopers that had/s the two turrets. He will be in a house...thing on your left, before you turn the corner to head towards that base.
His kit is on the rooftops.
When you enter the zone, b-line for the huge piece of saw machinery. Once you enter its "area" (from the right side), take your first right, and you can't miss him.
You kind of run into him, he will be next to like 5 of his dead buddies.