Yeah, a couple of ideas.
-First, you're dealing with a DC electrical circuit, and 2 things to keep in mind: 1) DC circiuts are very sensitive to bad solder/ mechanical connections, and can lose a lot of voltage if they're bad, and 2) You don't have a lot of voltage to loose. So, make sure all the solder connections are good, and that the mechanical ones (screws, contacts on the 3-way switch and output jack). are clean and solid. Be sure you have a good ground,too.
-Second, as I said before, pickup height plays a large part in getting good output. For most pickups, IME, too close to the strings can be just as bad as too far away. Gretsches, for example, are
notoriously sensitive to proper pickup height. I know; I have one. Trying to get a Gretsch's pickups just right can try a saint's patience. A lot easier on a Dano, but it
will take some fiddling and listening.
-Third, it's possible that the bridge pickup is just weak or bad. You can check the output with a multimeter (or have someone do it, but it isn't hard); it should be at least the same as the neck pickup. Also, it's possible that there's a capacitor in the bridge pickup circuit (like a Rickenbacker, for example), which will reduce the output. Not likely, but possible. If there is, removing it (or cutting it in/out with a switch-again, like a Rick) will help a lot.
-Fourth, and you won't like this one, is- that's just the way it is. Plucked strings have "nodes" along them, where the vibration (and potential for the strongest output) is. It's known as the Sweet Spot; that's why a P-Bass' pickups are where they are. Strings also vibrate least at the ends-the bridge and the nut. Danos, unfortunately, have the bridge pickup very close to the bridge. Rickenbackers do, too; "Why is my bridge pickup so weak?/Why is it so thin and trebly?" are very common posts on Rick sites. Proximity to the bridge is the reason. Ricks try to compensate with a hotter pickup there. Without a lot of success, even without the cap in the circuit; I have 2, and it's just the way they are. You can equalize the output with some careful fiddling with the volume controls; just mark the positions so you don't lose them! If it really bothers you, a much hotter pickup at the bridge is the only real solution, other than going to a single pickup in the Sweet Spot. Really, though, the whole idea of 2 pickups
is to have a different sound from each. How you blend them, and use one or the other, is what makes the arrangement so versatile.
