If you live in an area that undergoes a gradual but definite change of season, that is usually when such annoyances occur. Wood that's used to make your guitar is a living, breathing thing and is held together with glue, for the most part. As the wood expands and shrinks with seasonal changes in temperature and humidity bad things can and most likely will happen sooner or later. It doesn't matter if you have a $200 Chinese beater or limited edition custom guitar costing many thousands of dollars. Sometimes there's nothing to do but take it to a qualified guitar tech but sometimes you can cure or at least minimize the issues yourself. Here are a few common problems and some cures.
Now, understand that this is coming from a guy who scored a robust 15 of a possible 100 points on a high school aptitude test (what-are-you-going-to-be-for -the-rest-of-your-life kinda thing) in the section called Mechanical Reasoning. So if I can do some of these things, so can you!
Rattles are common as the wood changes. I've found that often this is caused by the adjustable tension rod in the neck. What's happening is that the nut or nuts on the end of the rod are not tight anymore, or perhaps the rod itself is moving slightly with the vibration of the strings. It's time to take a slight turn of the rod using something like a nut driver if the guitar has the adjusting point under a truss rod cover on the head of the guitar, or using a special long hex head wrench (available from Martin and Stewart McDonald) inserted in the hole you'll see in the top brace just inside the sound hole toward the neck of the guitar. Usually just a quarter or a half turn will do the trick; any more may adjust the relief on the neck to the point that the strings begin to buzz when fretted, or the action becomes uncomfortably high. Do this with tension from at least four of the strings. Otherwise you will not get a accurate adjustment.
If that doesn't do it, you may have a more serious issue, something like a loose brace inside the guitar. This is something that's hard to spot with the naked eye and is best left to a qualified repair person. That brace will need to be re-glued and clamped with special clamps designed for guitar repair.
You can usually determine is a top brace is loose by placing your fingers of one hand in various places on the face of the guitar as you strum the strings with the other hand. You can often actually feel the vibration of the loose brace.
The next most common annoying sound is string buzz - the sound of one or more strings bouncing on a fret that is not the one on which you are pressing down. There are many possible causes of this. If open strings buzz you may need a new nut or saddle or both. You can attempt this repair yourself by buying a pre-cut nut (measure the width - it will most likely be either 1 11/16ths" or 1 3/4" ) and carefully removing the old one, then gluing on the new one, or buying and replacing the saddle. Saddles are slipped into the slot in the bridge and should fit tightly but should never, ever be glued in place. Pre-made saddles are rounded on top at just the right radius so don't ever sand the TOP of the saddle; if it is too high you can sand the bottom but be careful and do a tiny bit at a time, re-inserting it often to test out the level. If you sand off too much you can make shims from thin plastic but this is not a preferred solution because using shims will dampen some of the string vibration and diminish the volume and resonance of your guitar. Both of these repairs can be done yourself but I much prefer bringing the guitar to a repair person who I know will "get it right."
Buzzes from frets are more difficult to identify and repair. Sometimes one or more frets will rise up slightly as the fingerboard wood adjusts to changes in humidity. Those bad boys can sometimes be found by placing a flat edge such as a metal ruler on the fingerboard - if it rocks back and forth you've found the culprit. Guitar techs use a special hammer to re-seat high frets and if you decide to try to push a fret back down using force, do it very, very carefully. Again, I would not do this myself but I know guitarists who have succeeded in this scary little operation.
The overall "relief" of the neck - the angle or bend - may have changed with the season. Take a long flat edge and place it on the first fret and the 14th fret. You should be able to barely slip a business card between the strings and the fretboard at the 7th fret. If you can't there is not enough relief in the neck and the truss rod will need to be adjusted because this is what's causing the buzzing. Some guitarists think a neck should be perfectly straight but this is not the case; there must be the slightest of bends in the neck to compensate for the up-down vibration of the strings. On most guitars, turning the truss rod nut clock-wise will straighten the neck, or give it less relief; turning it counter clock-wise will increase the "bend" or relief. In any case, keep some tension on the neck when you do this adjustment and turn JUST A BIT, then re-test the relief. Giving that nut a big crank will most likely only make things worse.
I almost always have to adjust the relief on my guitars on a seasonal basis. I invested in the correct wrenches and nut drivers and I'm glad I did because they make this little job fast and easy.
A few other things to be on the lookout for that unfortunately will need the skills of a professional to repair - so let's hope you never see them! One is a lifting bridge. Keep a close watch on the back of the bridge because that is where you'll see the first sign of lifting. If you see even the slightest gap there get your guitar to a repair person to be reglued and clamped or even replaced. If you wait on this it will only get worse and may even weaken the top to the point that the bridge plate inside the guitar begins to detach from the underside of the top - not a good thing. Also, be on the lookout for cracks beginning to develop anywhere on the body of the guitar. Fortunately, cracks can be avoided almost always by the use of a guitar humidifier. You should use one all winter long, without fail. Along with those things I run a room size humidifier in the studio all winter long. I do my best to keep the humidity level at 45%. Dryness if the enemy of guitars!
If you have questions about any of the things I've mentioned or would like a recommendation about dealing with them, drop me a line.
I hope these little tips help you avoid problems or deal with them if they crop up. It's enough of a challenge to play well - we don't need guitars that sound bad no matter how hard we try to have good technique.
Peace & good music,