Tele 4 Way (Series) Wiring Instructions
Step 1 First I remove the control plate and pick guard in order to remove the 3-way switch. You can see that I have added pin and socket connectors between the pickups and their connection to the pot (2 black wires) and the switch lugs (yellow and white wires). I have done this because it makes removing the pickups as well as the electronics much easier but it is not necessary or that practical unless you are modding the guitar a lot.
Step 2) Next I remove the three way switch. To do this you will need to de-solder all the wires which connect to the switch. I also remove the black, ground wires that connect to the volume pot (from the pickups) although it is only necessary to remove the black ground wire which is coming from the neck pickup.
Step 3) Screw in the new 4-Way Switch. To wire the switch I follow the same wiring that is shown in the above diagram. In pic 3 you can see that I solder a connection from the switch to the side of the volume pot. When it came time to screw the control plate back in I realized that the solder connection got in the way so I had to go back and re-solder the wire to the back of the volume pot rather than the side.
Step 4) I continue to solder the connections to the new switch just like the above diagram.
Step 5) In this step I break the connection between the neck pickups metal cover and the negative (black) wire which it attaches to. You can see the little metal connection to the left of the white and black wires. Then, solder a wire to the pickup-cover-lug (the dab of solder to the left of the pickups wires). The other end of this wire will go to one of two places, depending on where your guitar is shielded (like the guitar in the pictures) or if is not. If your guitar is shielded then connect the wire to the shielding material (aluminum foil in this case). If your guitar is not shielded than the wire should go to the back of the volume pot, like the diagram above.
Step 6) Lastly, I re-install the pickups and re-connect all of the pickups wires.
Check if the problem is described here, Troubleshooting Guitar Wiring.
If you still have not found the problem, I suggest you join this forum, The DIY Stomp Boxes Forum. It is an incredibly helpful resource that I have recently started to use when I need help troubleshooting. As long as you are polite and give a detailed description of the problem you are sure to get some valueable help within a matter of minutes. Most people on this forum are far more knowledgable about active electronics than I am and will be able to help you better and faster than I could.