leo_denmark wrote:I have now replaced my old, faulty sender with a C46272 from David Manners. This is supposedly a proper oil pressure measuring device used at older V12 and XK engines and not the on/off thing used for late XJ40 and X300.
I ended up with 90 ohm in series to get the same 6 bar oil pressure cold as I had before the change. I see a small pressure increase when revving it, but not much. I allowed the engine to warm up in idle, and the pressure dropped a bit to around 5.5 bar. I would have expected it to go lower, but a real drive will show if I get same readings as before.
My old sender would drop to zero at pressure below 3.5 bar, and that would not happen after quite some miles when RPM drops
With no resistor in series the needle moved out of the scale.
220 ohm in series resulted in 1 bar indicated at cold idle
Sender unit resistance at 0 bar: 330 ohm, dropping when pressure increases. Hard to do a proper test using a handheld compressed air gun...
I will update after having driven the car.
Conclusion is that I need a resistor a little bit smaller than 90 ohm, as oil pressure in warm idle now displays as 0.2-0.4 bar with the oil pressure lamp on. Another possibility is of course that my pressure has dropped to this level from around 1 bar during the 2-3 years of use with dead oil pressure sender, but I honestly don't think so