How to troubleshoot wiring problems

When trying to find that mysterious buzz, logic is your most effective tool

Don't give up, the problem is in there somewhere

Sometimes you might find yourself with a ground / buzz problem. This can be a truly frustrating experience and really kill the fun of building your own guitar. But, it really doesn’t have to be such a nightmare. You just need to trace your steps, that’s really it. This is all just logic. The problem is there somewhere, you just have to find it.

Assumptions:

In order to get around the fact that I am not actually sitting next to you as you work through this problem, I have to make the following assumptions:

You know what you are doing. (If not, don’t be too proud to march on down to your local qualified guitar repair tech, and as him to finish the job for you. Once they have done the work, you can always look under the hood and take a look at their handy work to see where you might have gone wrong)
All of your pickups are in perfect working order
Your cables and amp are in perfect working order

OK, now that that’s out of the way, here are a few suggestions:

Make 100% sure that you have soldered the ground to the ground and the hot to the hot. This is a very common mistake, and if you have mixed this up, all bets are off, nothing will quite sound right.
Make sure that your wires in your control cavity are not touching each other. For example, many Gibson Humbuckers have two wire leads where the ground is a braided wire on the outside and totally exposed, which can really lead to this exact kind of problem. But most single coil pickups have wiring that is sheilded all the way to the tip, which is helpful. Regardless, make sure that there are no ground wires touching hot terminals, and vice versa. It’s very common that even when you have done everything right, when you put the pick-guard (or tele control plate) back in place, some exposed wires touch, causing a ground or buzz.
Are you 100% sure that you wired the pots correctly?
Have you tried process of elimination? Simply wire each pickup directly to the main volume pot, bypassing the 5-way switch. In doing this, you can first determine that all 3 pickups are fine, as well as your pots. If you use this approach, you can deconstruct your wiring down to the most basic components, heck, even try wiring each pickup directly to your output jack. Trust me, if you take this kind of logical approach, you are simply going to find the problem. Anything else is just guessing, and you might be up all night doing this.

Some Common Wiring Problem Scenarios:

Everything Works, but the guitar squeals at minimal levels or with minimal gain.

Most likely, the main output wires are backwards. Open up the guitar’s main output jack, and reverse the hot and ground wires.

Everything works when the pickguard is un-screwed, but when I screw the pickguard firmly onto the guitar body, the signal cuts out.

An exposed ground wire is touching one of the hot wires or the pickup selector switch. Check all your ground wires and make sure that they are properly wrapped with electical wire and nothing is exposed.

Everything seems to work, but when I have my pickup selector switch so that two pickups are selected (an in-between position) the sound is really nasal-live, really weak and really bad.

The pickups are “Out of Phase”. Reverse the polarity of one of these pickups. Best to do it to an outer pickup (i.e. the bridge or neck position) because if you do it to a middle position pickup, it will just be out of phase with the other pickup that it is currently in phase with. Note that this sometimes results in a overly squealy pickup and sometimes pickups are simply out of phase and cannot be used together.

Things seem ok at first, but one pickup squeals a lot

The hot and ground wires are probably backwards. Reverse the hot and ground wires.

My volume pot works backwards. When I turn it clockwise, it gets quieter, and when I turn it counter-clockwise, it gets louder

The terminals are wired backwards. Reverse the way you have wired the two outer terminals. Leave the middle terminal as-is.

I have a humbucker pickup that should be dead-quiet, but it squeals and feeds back whenever I play with any amount of volume or drive

If your pickup has a nickel cover, then most likely you are experiencing micro phonic feedback. The only way to solve this problem is to have the pickup wax-potted by a professional guitar repair technician. Do not attempt to do this by yourself as you will most likely melt the pickup.

When I turn my guitar volume knob down even just a little, the sound gets muddy.

This is not a wiring problem. This is the natural behavior of the potentiometer. The potentiometer (or “Pot”) cuts off the volume at a certain frequency range, resulting in the muddy sound you here. Have a professional guitar repair technician install a “Volume Kit”. This places a small capacitor between your middle and right terminals. The end result is that the highs are maintained when turning your guitar’s volume knob down. This is a really worthwhile (and fairly inexpensive) modification that turns your volume knob into a very useful tool.

Summary

When I was younger I spent many many late nights pulling my hair out, trying to find out where buzzs and squeals were coming from. 99% of the time, it was something very simple that I overlooked. Rarely was it a deep and mystical issue. I promise that you will learn from this, and each time you wire up your guitar, you will get better.

Here is a schematic for a typical strat assembly. Not sure what kind of guitar you have, but I’m sure that if this schematic is not correct for your guitar, you can easily find one using Google:

http://www.guitarnuts.com/wiring/stockstrat.php

Jsut remember to be as logical as possible and retrace your steps. The buzz is in there, you just have to find it. Best to try removing as many variables as possible and isolating each component. You’ll be sure to find the buzz.