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> Oil pressure light on, but it's really dim, Replaced the pressure sender, it's still on
RoadGlue
post Jul 26 2006, 08:29 PM
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The other night I was driving the '74 2.0 home and I noticed that the oil pressure idiot light was on, but very dimly. I pulled over right away, checked oil level, turned the car to "ON" (not start) and noticed that the oil light was on, but was bright like you'd expect it to be.

I debated having the car towed, but I've had what I thought was a similar problem with a bad pressure switch on another 914 and decided to drive it home. The car drove normally and the engine sounded perfect, though the oil light was still dimly staring back at me.

Finally had a chance to swap out the sender tonight and it's acting the same way. Turn ignition switch to "ON" and it's bright. Start the car and it's on, but dim.

It's a very solid dim. No flickering or changes in luminosity depending on engine RPM. There's no engine oil spewing out when the car's on either. (IMG:style_emoticons/default/smile.gif)

I think there's a problem elsewhere. Obviously I need to make sure I have good oil pressure before driving it, and I'm going to borrow a screw in pressure gauge from my machinist friend before doing so.

With that said, what are the odds that I have low oil pressure? 914s that I've had before with low oil pressure had idiot lights that flickered, usually brightly. If it's an electrical problem, where should I start digging?

Thanks!
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lapuwali
post Jul 26 2006, 08:50 PM
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Try dimming your dash lights. Perhaps the gauge light is bleeding into the oil pressure "window".
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RoadGlue
post Jul 26 2006, 09:07 PM
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QUOTE(lapuwali @ Jul 26 2006, 07:50 PM) *

Try dimming your dash lights. Perhaps the gauge light is bleeding into the oil pressure "window".


Thanks for the suggestion! I tried dimming the dash lights, but it didn't make a difference.

Let's say I do have low oil pressure... could the light be half as dim as it is when the motor is turned off, but the switch is in the ON position?
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JoeSharp
post Jul 26 2006, 09:11 PM
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No, that light is getting power backfed somewhere. The oil light is on or off.
:PERMAGRIN: Joe
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RoadGlue
post Jul 26 2006, 09:54 PM
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QUOTE(Joe Sharp @ Jul 26 2006, 08:11 PM) *

No, that light is getting power backfed somewhere. The oil light is on or off.
:PERMAGRIN: Joe


That's reassuring, thank you!

Perhaps I can run a jumper from the sender to the light as a test... or does it go through a resistor? I'd better look at a wiring diagram before I get silly.
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Dave_Darling
post Jul 26 2006, 10:39 PM
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The sender is just a switch. It either grounds the wire going to it, or leaves it disconnected. Somehow there is something else hooked up there, but with a bunch of resistance...

I know the light behaves oddly when you hook up a sender for a gauge to it... Is your sender the stock one or the big fat cannister one?

--DD
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RoadGlue
post Jul 26 2006, 10:50 PM
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QUOTE(Dave_Darling @ Jul 26 2006, 09:39 PM) *

The sender is just a switch. It either grounds the wire going to it, or leaves it disconnected. Somehow there is something else hooked up there, but with a bunch of resistance...

I know the light behaves oddly when you hook up a sender for a gauge to it... Is your sender the stock one or the big fat cannister one?

--DD


Hi Dave!

It's the stock type. The rellocation hose for the big pressure sender cannister is on its way from aircooled.net now, so those *fancy* bits are still sitting on the shelf.

OK, I think I feel comfortable driving the car now. I'll try to track down the source of the bleed-through this weekend.

Cheers!
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RoadGlue
post Jul 27 2006, 12:21 PM
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So there is certainly some bleed-through happening here. I disconnected the wire at the pressure sensor and the dash light is still dimly on. Whew. This car has a few spooky electrical issues that I need to sort out.

Thanks everyone!
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Brad Roberts
post Jul 27 2006, 12:25 PM
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Check all the grounds on the back of the gauges.

Make sure and pull all the other "bulbs" out of the back and clean them also.

B
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RoadGlue
post Jul 27 2006, 12:32 PM
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QUOTE(Brad Roberts @ Jul 27 2006, 11:25 AM) *

Check all the grounds on the back of the gauges.

Make sure and pull all the other "bulbs" out of the back and clean them also.

B


Do you *really* think there would be grounding issues on this car? It *only* sat for four or so years, outside... neglected... unloved. (IMG:style_emoticons/default/wub.gif)

OK, I'll check 'em. I seem to recall that the turn-signal indicator light comes on dim from time to time too. I'll pull the gauges and fuse block and clean all that up.

Cheers,
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