oil pressure gauge shows backwards

[AndersL]

I have a S4 from 95 with Caerbont gauges, the oil pressure gauge 0-7 bar has always (since I bought it) shown the oil pressure backwards, which means it starts at 7 bar and then drops a little when the engine gets hot. I have checked the oil pressure manually and that is what it should be, the gauge Only display strange.

Now I have checked the gauge and it shows high pressure at low resistance but the transmitter in the car sends low resistance at low pressure. so it is obvious that the transmitter in the engine is not suitable to the gauge.
Someone has mounted the wrong transmitter, I have to find a transmitter that gives high resistance at low pressure so that the Caermont gauge shows the correct pressure.
There is a transmitter in the car today with both pressure and warning contact (see link), I have found in lotus partlist that my S4 apparently should have had transmitter (without warning contact ) A082N4038F if the car has Caermont gauge and separate warning switch, but I cannot find a non used warning switch or a place where it has been sitting.

I need to have a transmitter that gives high resistance at low pressure and a separate warning switch.

i hope this make sense for someone so i can have some helppartlist.pdf

The question is:

which transmitter/sender ?
which warning switch ?
where is the warning switch located on my engine ?

Sender in the car today (pressure and warning contact) A082N6062F
https://www.sjsportscars.com/parts-and-accessories/B082N6062F.htm

Sender (only pressure) A082N4038F
https://www.sjsportscars.com/parts-and-accessories/A082N4038F.htm

Low oil pressure switch (V8) A082N4039F
https://www.sjsportscars.com/parts-and-accessories/A082N4039F.htm

[CarBuff]

This Topic shows the location of the sender and warning switch, on the LR side of the engine block.  I bet someone installed a VDO sender instead of the proper Caerbont type.

https://www.thelotusforums.com/forums/topic/98070-oil-pressure-oddness/?do=findComment&comment=806056

 

The senders rely on a good ground-path so perhaps assuring a proper earth will resolve your issue.

 

(IIRC there is also a relay involved that prevents the Low Oil Pressure lamp from illuminating during hot idle...)