Guitar wiring/electronics issue

[u/How2Soul]

Hi! Having some electronics issues, would greatly appreciate any thoughts or suggestions. I followed the attached wiring diagram for an SH configuration. I used the option shown in the box, and also added a resistor (going from neck pickup to ground) so the single-coil pickup sees the pots at around 250k.

The issue:
- It was working fine for a few hours and then started acting up
- All positions now sound like the high end has been filtered out, as if the tone knob is rolled all the way down. However, that’s with the tone knob wide open, and it gets darker as I roll it down (tone pot behaves normally, but overall tone is incredibly dark and muddy, not how it was at first)
- Volume does not completely cut when I roll the volume pot all the way down. There is still audio coming through when the guitar should be completely silent

Relevant observations:
- The middle position (and the humbucker) are noise canceling as expected
- Because the guitar sounded normal at first, I don’t think it’s a matter of wiring it incorrectly. it’s not the cleanest job, but I made sure all connections are secure and used heat-shrinking tubes (and some blue tape) to keep any exposed wires from touching each other

Has any of you encountered this particular set of issues before? I’m wondering if the volume pot is broken internally, which could account for it not going silent when all the way down, but could that also be darkening the tone of the guitar?

Thanks

[u/OsoSuhr]

Don’t overlook the quality of the solder connections. A connection can look fine and still be intermittent, especially if it wasn’t properly wetted. I’d also check for stray strands or unintended shorts.
Some 4-pole, 5-way switches can develop contact issues, even when they’re relatively new. I’d check continuity through each switch position with a meter rather than assuming the switch is good.
The volume not shutting off completely makes me particularly suspicious of a bad ground connection at the volume pot. I’d check that first. The excessive high-frequency loss could be a separate issue, possibly an unintended load or partial short.
The fact that it worked initially doesn’t necessarily rule out a wiring or soldering problem.

[u/norm-1701]

I like the way you phrased your issue and your question, all the relevant information provided with details.
I can't add much more to the answer that u/OsoSuhr provided which is also very good.
Two suggestions:

1. As a test, I would disconnect one pickup and test the tone to see if it is what you expect. Then try the other alone. Trying one pickup at a time will tell you if the issue you see comes from both being connected at the same time or if this not the case, it will tell you which one is dragging your tone down.

2. It's probably good but please check that the resistor is in parallel and not in series (from the hot-white to the ground). It is a 470K resistor, right?