I had to replace my oil pressure sender today and in the process learned a few things that, collected in one place, might help others.
1. To easily remove the switch, a thin walled 25mm socket is required. A 1" Whitworth socket, also thin walled will do the job too.
2. The thread on the switch is ⅛" BSPT, or 28 TPI.
3. When screwing in the replacement, I struggled to get it past ½-way. Not having a suitable tap, I cut a vertical slot in the old switch and used this to clean the threads. I was surprised and the gunk that came out, but thereafter I was able to screw in the new switch by hand.
4. The switch doesn't have to go in all the way, so a torque value is not available. Just do it snug, so you don't need that socket again.
5. I used a doughty washer rather than a copper/steel one as here is a bit of taper at the bottom of the switch, meaning a washer wouldn't sit flat. The doughty washer has a rubber inner which I thought might do a better job. I also used a little thread sealer, just in case.
6. Getting that little bolt back in the top to secure the wire is a bu*!#r!
Good luck.
