Oil Pressure Light

I am getting a red oil can light come up on my 300tdi Disco Was wading yesterday in Terling Ford and it happened on the way home after I got off the A12 travelling at 70mph down to normal roads at 30mph.

When I first noticed it, it was on permenantly then 20 mins later it was flickering on and off quickly. Now after a run the oil light comes on when I take my foot off the accelerator. Soon as you accelerate again it'll go off

I can only think that it was the water caused damage to the sensor or the top up I did yesterday of 10w40 has triggered something. Can't think of anything else :doh:

Can anyone enlighten me? A solution would be nice! It can't surely be serious or the engine would have exploded by now

Btw, I haven't changed the oil since I had it (since this January) so I don't know what is in there, just topped it up with 10w40 every now and then.

Water won't cause the oil pressure to malfunction although the electrical connection can be iffy and oil grade would not have "triggered something" as always the first thing is change the oil pressure switch and go from there.
Sorry but then it gets serious with oil pumps and other stuff.

By taking the oil pressure switch out, is oil going to flood out?

I have disconnected it a little while ago and cleaned out connection which was full of black ****. Hoping that is what it was.

Does the pressure switch screw in like a spark plug?
If not I'll change switch and oil along with filter.

oil pressure switch can be unscrewed easily and replaced worth checking pressure with guage while off as is test point as well if you cant fit new one and if goes out straight away and comes back on a little after engine turned off with ignition still on not bad pressure