335 Pickup wiring troubleshooting

[Jordan86]

New here. Working on a friends guitar for him. It’s a hollow body which Ive never worked on. Im more of a tele and strat guy. Looking for advice on troubleshooting and knowing how to hone in on the issue.

The first observation was that the neck pickup did not work. On the pickup selector switch, I get bridge (bridge), bridge only (middle), nothing (neck). So I pulled the switch out of the F hole and fiddled with it. No change. Thinking the switch might be bad, I jump the contacts from neck pickup to output, basically bypassing the switch contacts. Still no neck pickup. But thought I heard something. So I cranked the amp and got the tiniest faint signal possible. Enough to tell the volume pot would turn it off and on. And the tone control seemed to respond too, albeit still a very faint signal.

Wondering if the volume pot could be the culprit? It’s a push pull pot with a 4 pin quick connect. Not sure though. Maybe a dead pickup?

Any other troubleshooting tips? It’s just hard to get in there to know what to check, let alone get a multimeter in there.

[The Dude]

What is the resistance at the output jack when the switch is in the neck position and the volume is at max? You're probably going to have to get enough guts out to make a measurement of the pickup itself, but I'd start there. A little tip, if you have to remove pots, switches, etc. tie a string around the pot shafts and leave the string hanging out the topside. It will make it easier to reassemble and guide parts back into the holes.

[Jordan86]

Was just doing this, since I figured someone would ask. And figured I should know. I’m getting....

bridge: 8.4k
middle: 8.25k
neck: 509k

very strange. Neck reading is the same (509k) with or without the coil tap. Bridge reading with coil tap is 4.2k. I think it’s definitely something with the neck pickup or volume pot.

[Jordan86]

Also tested the switch positions for proper continuity and it seems to be working as intended. My reading on the middle selection would indicate that as well. 8.4k in parallel with 509k would be 8.25k

[The Dude]

"neck: 509k" would likely indicate an open pickup or a broken connection. Unfortunately, it's surgery time.

[Jordan86]

Thanks, Dude. Happy days. So a few questions before I dive in....

1) The push pull volume pots have this quick connect and pcb attached to the mini 500k pot. See here https://www.ebay.com/itm/283448610936
I don’t think it will fit out the f hole. Do I need to pull the bridge pickup and pull everything else out through that slot?

2) Does EVERYTHING need to be pulled? As in the entire wire harness? I imagine there’s not enough slack to just pull the neck pots.

3) If I could manage to just pull the quick connect off the back of the neck volume pot, I could hypothetically measure the pickup with those contacts to confirm whether it’s a bad pickup or the connection is breaking at or after the pot? I guess that wouldn't change the inevitable though that I’ll still have to go fish.

[The Dude]

If you can get the neck pickup connector disconnected from the pot, yes of course you can measure it at the connector. Maybe if you also remove the bridge pickup you can get your fingers in there to unhook the connector? I don't have the guitar in front of me, so you'll have to figure out what works. That said, my policy is always to disassemble only what's necessary to do the work.

[Mick Bailey]

I use an adjustable dental mirror and LED torch to assess how to go about a repair on these guitars. Sometimes if they've had any previous work done the wiring can be twisted up and not as straightforward. Dental floss is pretty good to tie onto pot shafts so they can be pulled back into position. It's sometimes possible to work on pot connections through the F-hole without completely pulling them out of the bridge pickup access and it should be easier with the quick connections. Getting everything back is usually difficult either way, though.