The other guitarist in my band bought a new Jackson Dinky with stock pickups. He decided to put in some EMG's and had the tech at the local music store put them in and they sound great! (to him at least). The only problem is that the volume knob is completely useless and unless he's playing it, it produces an awful menagerie of beeping, hissing and roaring. What's the problem and how can we fix it?!
What's the problem and how can we fix it?!
I wouldn't try anything. Have him take it back to the tech who worked on it and have them fix their mistake. They should have switched out all the pots and output jack. As well as completely re-wired the guitar.
But you could start out by taking the backing plate off and checking to make sure there's no loose or broken wires that you can see. If it's a kit that needed to be soldered together, check all the solder points. If it's a kit with the quick connectors (or whatever they call them), check to see that they're all plugged in properly.