Oil Pressure Light Switch

[geodon]

I have a dimly glowing oil light at normal revs.

My experience of these is that a hot line goes to the dash light & is then earthed via the switch when the oil pressure drops.

But that does not seem the case with Holdens.

My HQ manual has no wiring diagram.

Can anyone link me to what I need for a diagnosis? I don't think it's anything sinister, the eng is quiet. If the pressure is down, the bearings would rattle. I hope!!

[hesguitar]

This picture is from a vc commodore manual and shows the switch to ground from hot which is how i wired it and it seems to work.

Switches fail, common on new commodores actually, but so do oil pumps! I'd either just get a new switch (cheaper than a pressure gauge if you don't have one) and see if it fixes it if not get a gauge and check the pressure, if the pressure is good check for earth leaks, though if the light goes out at higher rpm the latter is unlikely.

[bee utey]

Maybe you've got a VDO oil gauge pressure sender instead? How big is the "switch"? Disconnect the wire, if the light goes out get a new pressure switch.

[geodon]

Well done Bee Utey!!

Actually, I thought the damn thing looked familiar! It's twice the size of a switch so it must have a bellows or something. I've seen similar on air cooled VW's with added oil pressure guages.

This car did have an added oil guage. I will dig it out & investigate.

[debruiser]

I have just discoverd I have a similar problem! Had the rocker cover off to renew the seal, and had the oil pressure sensor wire off.... forgot to put it back on :wasntme:. found it yesterday... stuck it on... now the oil pressure light doesn't go out! :mad: (unless I unplug it). first step - buy a new pressure sensor?

I've driven about 600kms since I had the rocker cover off so I doubt that the oil pressure is low....

[geodon]

The feed to the oil pressure switch is hot ie live when the ign is switched on and it goes via the Idiot Light on the dash to the sw on the block.

With zero oil pressure, the line is earthed via the switch and the the light goes ON. As oil pressurises, it breaks the connection to earth and the light goes OUT.

If it's on all the time then the connection to earth is permanent eg:

* constant low oil pressure
* the wire to the sw has frayed & is touching something ( happened to me on an air cooled VW. Took weeks to find!)
* The Idiot Light holder is earthed

DON'T BUY ANYTHING TILL YOU'RE SURE!

Have you a circuit tester? eg an old 12 light socket from a discarded tail light? Hook one lead to your battery +ve then touch the other to earth. The light should go ON.

Then attach to the sensor. Engine stopped, light goes ON If the light goes OUT when eng is running, your sensor is fine. Look for something else.

[geodon]

Don't buy anything till you're SURE!

Have you got a circuit tester? An old 12V light socket eg a tail light?

Hook it up to the battery +ve then touch t'other lead to earth & the light should go ON. Now test your oil pressure sensor. Engine not running=ON Engine running = OFF would suggest your sw is OK.

[Stuck]

I have just discoverd I have a similar problem! Had the rocker cover off to renew the seal, and had the oil pressure sensor wire off.... forgot to put it back on :wasntme:.


Are you sure you're referring to the correct switch ?. The oil pressure switch is the one near the oil pump, the temperature switch is the one in the head which to me would be the one more likely to get disconnected when removing the rocker cover.

Cheers,
Anthony.

[debruiser]

Are you sure you're referring to the correct switch ?. The oil pressure switch is the one near the oil pump, the temperature switch is the one in the head which to me would be the one more likely to get disconnected when removing the rocker cover.

Cheers,
Anthony.

Anthony, I know what you mean. But I have a feeling that my conversion was a real 'back yard' job. the wire for the oil pressure is strapped to the wire going to the temp switch. they must have thought that would look neater....

But no I mean the Oil switch.

was going to attach a picture... but it doesn't want to co-operate

[debruiser]

O loo at that! It did work! wow

[Blknight.aus]

the switch can also become intermittant or oil fouled, once that happens its not far off leaking.

to check that you really need a decent multimeter OR a range of bulbs.

if you test it with one thats of higher wattage than the one in the dash you may get a false OK as theres not enough current passing through the switch to light up a bigger bulb.

theres also a varying range of pressure sensors that will fit look about the same and work pretty close to right and will give the same symptoms if you hook up a light instead of a gauge.