Hi all, first post here!
Well, actually it's my second post as I did a lengthy write up last night on this, complete with linked images and of course I wasn't even thinking that the pics were technically links to other sites so it got trashed as spam. Anyway I'll do a slightly modified write up here and just give you some terms to search so you can see what I'm talking about.
For a start, while I can't compare the actual terminals I believe your switch is a "Carling TIGK51-6S-BL-NBL" but I suspect the actual part number is on the opposite side of your switch.
However, it looks to me like your switch is wired with 2 "single female to dual male" adapters on the red & purple wires. These can be problematic and I'd suggest giving them a good off-and-on and then a good wiggle afterwards to see if your problem goes away. If it does I suggest crimping up your own "Y" adapter with a single female and dual male plugs on about 2 inches of wire, it takes a lot of strain off the terminal. Also if you don't have any yet a tiny dab of silicone grease protects a bit from future corrosion but more importantly makes the little bastards a lot easier to push on and remove.
I believe the 3126 also has a "Bosch style" 12V relay that energized the shut off solenoid and those can go bad, the ones you buy at an auto parts store are the same as the ones you get at a boatyard except cheaper, buy one from napa and they're about $15 but online at places like walmart &ebay you can get a pack of 4 or 5 for that. Quality seems to be the same, if for piece of mind you'd like the "best money can buy" I'd say purchase a genuine made in Germany Bosch one.
Lastly, on your pic of the switch it looks like the purple wires and 2 of the red wires are switched to each other, and the yellow/red stripe is switched to the other red wire in the pic but I cannot see if that wire even goers to this switch? I'm assuming it does but please post if it doesn't.
Anyway, hope everyone is having a happy Easter!
Mark