AAZ oil pressure problem

[halfbakedpixels]

Was driving home from Norwich last night in the horrible weather and noticed the oil warning light had come on. So I pulled over into a garage, but noticed as soon as the engine goes to idle the light goes out. If I rev it the light glows brighter.
It's an AAZ engine with an oil pressure sensor in the oil filter housing and one in the head. A lot written on the net suggests both are normally in the filter housing, but one of mine is blanked off.
Anyone shed any light on this issue?
It seems to run okay and the oil level is fine.
I recently changed the inlet manifold for an AAZ type instead of the JX one that was fitted, also re-routed the turbo piping to accommodate for the different inlet manifold pipe orientation. But I don't think that should make this happen?
Would love anyone's input.

[colinthefox]

I hope this bit of logic might help track down the problem. Either the oil pressure warning system is working, meaning you have an oil pressure problem, or it's not, in which case you have a problem with the oil warning electrickery.

Based on what you've said, my money would be on a problem with the electrics, if it was a problem with oil pressure, and the warning was working OK, the light would be on at idle, and off when you rev the engine, not varying in brightness.

You could pull the connector off the switch on the head, and the light should go out. If the light stays lit, it's a problem with the electrics. Once again if I were a betting man, I'd have a look at the earth crowns behind the glove box (on RHD), or the 14 pin connector to the dash PCB for corrosion, but earths from engine to chassis could also be to blame. If the light goes out completely when you disconnect the switch, then it could be the switch itself. I've had two switches recently go weird when oil has leaked into the switch mechanism, causing high resistance.

We'll ignore the "buzzer of doom" circuit for the moment to avoid complications.