Oil pressure warning lamp
Discussion
I changed my engine oil about 1000 miles back to a very topical Mobil 1 15w50 Fully Synthetic. Having only had the car a month or so and being a sad engineer I wanted to know that the life blood of my little baby was good. I know that "what oil to use" is a topical subject altogether but my question doesnt relate to oil type at all but may be relevant.
Oil pressure although no actually physically meassured appears around 30 psi when up and running at about 90 degrees. Not once has it droped below 20 (even during the extreme summer). At start up pressure is around 50 - 60 psi as you would expect and watching the gauge drops nicely. However - the oil pressure warning lamp can flicker sometimes and it appears to be getting worse - however this may be due to the amount of driving done in darker conditions making it more noticable.
I know you should stop the car when it illuminates but I think this is a switch/earthing/wiring issue. The bible shows that the switch is a Normally Open design (with ignition off). Does anybody know at what pressure this switch opens? Has anybody come across this issue. Oh its a 4.0.
Im off down the garage to test the circuit myself now but any ideas about the switch issue would be appreciated.
Oil pressure although no actually physically meassured appears around 30 psi when up and running at about 90 degrees. Not once has it droped below 20 (even during the extreme summer). At start up pressure is around 50 - 60 psi as you would expect and watching the gauge drops nicely. However - the oil pressure warning lamp can flicker sometimes and it appears to be getting worse - however this may be due to the amount of driving done in darker conditions making it more noticable.
I know you should stop the car when it illuminates but I think this is a switch/earthing/wiring issue. The bible shows that the switch is a Normally Open design (with ignition off). Does anybody know at what pressure this switch opens? Has anybody come across this issue. Oh its a 4.0.
Im off down the garage to test the circuit myself now but any ideas about the switch issue would be appreciated.
Nick P said:
my pressure show 15 psi when the engine isnt running and the ignition is on....it shows 60psi when cold then drops to 20psi when hot.....does this sound like my pressure switch could do with replacing?
(The fact it registers a value when the engine is not running)
(The fact it registers a value when the engine is not running)
This isn't right. It should read zero with the engine stopped, so you can already assume that the gauge is reading 15PSI too high. Although it isn't a scientific comparison as they're all different and many factors affect oil pressure, mine reads 45PSI when cold and revving. This just happens to be a 15PSI difference too.
Now, your 20PSI when hot may actually be more like 5PSI. This would suggest the switch is working and there's another problem. Best to take it to a garage and have it checked properly. If there really is low oil pressure, it's not the best time to mess around with sensors just to eliminate them.
Cider Andy said:
Nick P said:
my pressure show 15 psi when the engine isnt running and the ignition is on....it shows 60psi when cold then drops to 20psi when hot.....does this sound like my pressure switch could do with replacing?
(The fact it registers a value when the engine is not running)
(The fact it registers a value when the engine is not running)
This isn't right. It should read zero with the engine stopped, so you can already assume that the gauge is reading 15PSI too high. Although it isn't a scientific comparison as they're all different and many factors affect oil pressure, mine reads 45PSI when cold and revving. This just happens to be a 15PSI difference too.
Now, your 20PSI when hot may actually be more like 5PSI. This would suggest the switch is working and there's another problem. Best to take it to a garage and have it checked properly. If there really is low oil pressure, it's not the best time to mess around with sensors just to eliminate them.
however the oil warning LED never comes on (apart from engine off!!)....when i crank the engine over the light goes out so i presume my oil pressure is good......possibly a cranky gauge?
Nick P said:
my pressure show 15 psi when the engine isnt running and the ignition is on....it shows 60psi when cold then drops to 20psi when hot.....does this sound like my pressure switch could do with replacing?
(The fact it registers a value when the engine is not running)
(The fact it registers a value when the engine is not running)
Me too. I get 5psi by switching ign on. I don't think it reads 5psi too high though....... Probably a dodgy contact. I get around 20psi when driving at normal temps, seems OK to me and never seen the light flicker.
With ignition off the gauge should read zero -ignition on but not running the gauge should read max pressure. As the pressure decrease so does the resistance - I think. I feel a multi meter moment coming on as well as a switch replacement.
Next question off the top of anybodys head switch PN???????????
Next question off the top of anybodys head switch PN???????????
Back from the garage and I am now confused 
multi meter equiped thought I would start to get my facts correct for my car. Starting with the oil pressure switch. Ign off switch closed warning lamp on - so far so good! After testing several senarios - too dull to explain I have come to a rather confusing conclusion. My oil pressure lamp on the dash has been miss wired and is actually the alternator not charging lamp. The orange lamp (middle one) is incorrectly the oil pressure switch lamp. Verified by shorting to earth through multi meter and it glowing - shorting to earth direct and it coming on.
Conclusions at this stage. And thanks to everybody who assisted - my round!
I dont have an oil pressure issue at all - thank didgery do for that
I do have a issue behind the dash - not to worried at this stage
My alternator may be on way out again - more multimeter action I recon - check to see what voltage and amperage the old girl is putting out.
multi meter equiped thought I would start to get my facts correct for my car. Starting with the oil pressure switch. Ign off switch closed warning lamp on - so far so good! After testing several senarios - too dull to explain I have come to a rather confusing conclusion. My oil pressure lamp on the dash has been miss wired and is actually the alternator not charging lamp. The orange lamp (middle one) is incorrectly the oil pressure switch lamp. Verified by shorting to earth through multi meter and it glowing - shorting to earth direct and it coming on. Conclusions at this stage. And thanks to everybody who assisted - my round!
I dont have an oil pressure issue at all - thank didgery do for that
I do have a issue behind the dash - not to worried at this stage
My alternator may be on way out again - more multimeter action I recon - check to see what voltage and amperage the old girl is putting out.
Cider Andy said:
Nick P said:
the oil pressure warning lamp can flicker sometimes and it appears to be getting worse
Nick P said:
however the oil warning LED never comes on
My apologies if I'm missing something here: are there two warning lamps on your car?
the first quote isn't mine!!! it's symonabs
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