Oil pressure light..depending on outside temp
 

I come to ye ol' super smart Mini people most humbly...

So I can usually google most of what im looking for, but this one has me stumped, so i come to you all to get some clues to my problem.
1st the car...2004 R53 JCW, 112k miles.
2) recent(ish) maint: oil change, SC oil change, harmic balancer replaced, air filter, alt, plugs&wires.

Now...the problem. <49°f (maybe 50°) engine hot or cold---oil pressure light on when under 1300rpm. >50°f(maybe 51°) engine hot or cold--no oil pressure light. I can see it happen as the temp rises or drops on my way to work or on the way home, or just driving (51° to 47°) then as i come out of the valley back up to >50° it doesnt come on.

Ive checked for crushed filter, the check valve thing in the oil filter housing. I have not checked the actual oil pressure at sensor yet...thats next.

Suggestions, ideas? TIA
Matt

It might be a loose wire. When cold, the metal is contracted and a good connection made. As it warms up, the metal expands and may lose contact, Just a thought, based on temperature.

Thanks, ill look at those today when it warms up.

The key factor here is that it happens when ambient temp is below 50F, even with engine fully warmed up - correct?

Then I think you can rule out engine compartment thermal expansion / oil viscosity as causes.

Does it also fail when the cab in temp is warm?

Maybe something going on in the electronics.

cab can be hot or cold. Heat on blast or off. I havent been running the AC since its not warm enough. But, ill see if maybe im not paying attention to this factor

When you get a chance to poke your head into the engine compartment, take a look at the sensor connection and see if it appears oily. If it's oily, chances are the sensor is likely not in a good state. The sensor sees a lot of heat and vibration living where it does.

After 15 years, it may just be an age / time to replace issue. We replaced the sensor on my kid's R53 when the car had 227K and presented similar symptoms as yours. Since replacement, we have not seen the light come back on.

...and I did see it, but your oil level is full, correct?

Ill look and see if there is residue.

as for your last question, yes, ive checked a few times, it hasnt gone down since i did the oil change a few weeks ago.

from most of the replies, i hope its just the sensor issue not the oil pump.

There was some weeping around the sensor, gonna replace that and go from there. Any suggestions on where to get one...way, ecs, amazon ect?

My oil pressure light would randomly come on some times. Turned out to be the wiring from the sender was rubbing on something where it ran down along the starter.....it was shorting out, and giving a false reading. After I fixed the spot where it was rubber through.....it was back to normal.

Just something to check.