Warwick basses have the most reliable necks. The person who told you that was probably too stupid to read the manual and take good care of his bass. Trussrod adjustments are described briefly and accurately right there. The most important thing when making a trussrod adjustment on your bass is to ask yourself: "Does my bass need a Trussrod Adjustment?"
If the answer to that questions is YES, then you start trying to figure out how to make the adjustment, and if you don't trust yourself doing this on your own, please take your bass to a qualified luthier (you'll thank me for this piece of advise later). So, getting back to trussrods, to find out if your bass truly needs a trussrod adjustment, you need to ask yourself a few questions:
ACTION TOO LOW:
1. Where am I getting fret noise?
a. 1st - 4th fret = You need to raise the nut a little bit.
b. 4th - 7th fret = You need to loosen the trussrod.
c. 7th - 24th fret = Adjust the bridge.
ACTION TOO HIGH:
1. Apply the same concept as before. Only take into account that in this case, if the action is too high between the 4th - 12th fret, you will need to tighten the trussrod instead of loosening it.
So, if you are asking yourself why would you need to loosen then trussrod to raise the action, here's the answer, the trussrod is there basically to create balance between the pressure created by the strings pulling on the headstock of the bass. This makes the neck bend a little. So, if the action on your bass is too low, this means that the neck is a little too flat, and you need to loosen the trussrod, to let the strings pull a little and create some pressure that will raise the action. In the case that your action is high, you would want to do the opposite, meaning you'd want to tighten the trussrod to flatten the neck some more.
Right now, Warwick Trussrods work in the same way as a regular screw: if your turn it clockwise it will tighten, and if you do the opposite, it will loosen a little bit. When adjusting the trussrod on your bass, you need to know a few things:
1. A little bit goes a long way. Turning the trussrod an 1/8 turn would be a good place to start. After you do the first adjustment, let the bass rest for a few hours so that you can actually notice the change. If you turn the trussrod too much, after a few hours when the wood adapts to the adjustment you just made, you might even break the neck, so do it slowly and in small increments.
2. Drastic Humidity changes can cause the neck relief to change, as wood absorbs humidity in the air and it adapts to that environment, so when you travel, your bass might need a little adjustment, but never too much.
I hope this helps you understand a little better how Warwick Trussrods work and understand probably why the person who told you that had absolutely no idea what he was talking about, since for any bass player in the world, Warwick makes the most adjustable basses out there, giving the player the opportunity to adapt his instrument to the way he plays, and the trussrod is a big part of that. As a person (and bass player) that works for Warwick, I have to say that we have received some broken trussrod issues in the past, but VERY FEW cases because of a defective trussrod, most of the times it was because of the bass being adjusted by someone who was not a professional and didn't know exactly how to do the job. I hope that covers it a little better, but if you ever have ANY questions about this, or if there is something that I didn't explain well enough, please shoot me an e-mail and we'll get it sorted out.
