Oil Pressure Light Always On

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DCMotoring
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Joined: Thu Nov 12, 2009 5:07 pm

Oil Pressure Light Always On

Post by DCMotoring » Thu Oct 17, 2019 5:10 pm

Tested switch and replaced just in case. The oil pressure light is on regardless of whether it is connected to the switch. Solid light, does not flicker or respond to any changes in oil pressure/RPM.

Tracing the wire from the switch, it goes into the engine harness and into the fuse box and from there to the instrument cluster. Am I right to think the wire is grounded somewhere along the way? If so, is there any particular place I should check?

Note: This happened right after I replaced the starter, so I don't know if that is related at all. I wouldn't think so, but with these old electrical components you never know.

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Lock
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Location: Washington state
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Re: Oil Pressure Light Always On

Post by Lock » Mon Oct 21, 2019 10:33 pm

Do you also have the "oxygen sensor" light in the middle cluster above the center vents?
The oil pressure signal is also connected to that, so that it comes on to test. That wire comes out from on the firewall near the pedal assembly and down under the drivers side frame rail to the counter box. It may have been damaged/grounded during your work.

Unplug your engine connector from the fuse box, turn the key and see if it stays on when not plugged in. That will tell you at least if it's on the engine side (likely due to your starter work), or in the dash.

At worst you could run a new wire from the engine connector fuse box plug over to the oil pressure sensor.
1979 528i 5-speed conversion G260/6, Motronic 1.3 179
1980 Honda CX-500

DCMotoring
Posts: 12
Joined: Thu Nov 12, 2009 5:07 pm

Re: Oil Pressure Light Always On

Post by DCMotoring » Tue Oct 22, 2019 1:22 pm

I do have the oxygen sensor light, but the emissions equipment was removed when I purchased the car. I'll have to dig around to see if there is a wire down there but I did unplug the engine connector and the light was still on so next step might be to remove the instrument panel and follow the wire through the mess under the dash. I have ordered a mechanical oil pressure gauge so either way I'll have a solution soon. Thanks for your help!

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Lock
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Re: Oil Pressure Light Always On

Post by Lock » Fri Oct 25, 2019 12:16 am

That's a tough one. The counter box just counts the speedometer cable turns, and eventually turns on the light after (I forget how many) amount of miles to indicate that the O2 sensor needs to be replaced, so it's really just a mileage indicator and even though PO removed emissions, I'd guess it got missed as it's hiding under the drivers floor. Plus given your recent work was on the starter, I'm going to guess that the wiring to it, if it still exists, may have been disturbed. Especially if it was cut and not terminated properly.
But if it's not that, maybe just by coincidence one of the wires in the dash has shorted out. To get the instrument panel out you unfortunately have to take the steering wheel off. I just take the whole steering column/indicators/ign key assembly off as one piece (after marking the alignment on the column), it gives you plenty of space and I think that's what the books recommend.
The wiring for that goes immediately left over to the firewall in there, so tracing it should be simple. There's a metal "shelf" in there so you can't really get to it from underneath.
1979 528i 5-speed conversion G260/6, Motronic 1.3 179
1980 Honda CX-500

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