Lancia Motor Club

Please could anyone tell me why my oil pressure gauge increases its reading by a few psi when I turn the headlamps on full. I can understand why it might drop due to a reduction in voltage, but why would it increase?

Perhaps the electrical connection to the lights is also adding to the oil guage circuit? Is there anything else positively altering?
Richard

Nothing obvious. The headlights are supplemented by 2 spotlights (rather nice slim Cibie Iode 45s) that automatically come on when main beam is selected. That means all six 55W halogen bulbs plus side lights, ignition circuit etc. draw more than the alternator gives out!

I intend to replace the halogens with LEDs when I get around to it, but the car is rarely driven in the dark.

I assume, perhaps wrongly, that the sender is a type of rheostat and as the oil pressure increases so does the voltage..

I think sender variable resistance with temperature and with the gauge it is a whetstone bridge circuit so should not be voltage dependant?

I’ll have to study the article about that which I’ve just found. Definitely going back to my school day physics classes which was a very long time ago! My understanding is that most car oil pressure senders use a rheostat set up.