I wired up my friend's Tele with the 4-way switch and I was surprised by what I heard.
Position 2 (both pickups in parallel) is skewed towards the neck pickup, same volume as single pickups. Darker than a normal Tele.
Position 4 (both PUs in series) actually sounds like position 2 in a normal Tele but louder.
So I checked my wiring, solder joints, grounding, continuity. I also looked at how the switch works to make sure it was actually doing its job. All good.
I did some reading and apparently pickup order affects the series position. Bridge first (my case) sounds brighter, neck first muddier - what I would expect.
Does that make sense to you?
On a good note, the Pinecil does work on the back of pots but I have to use the knife tip and the boost function - besides running hotter, it gives the iron more power.