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Hello all,
I am try to figure out why my oil light flickers off and on. I had a leak from my oil pan drain hose, but fixed that. Before that the oil pressure light stayed on while running engine at higher rpms. Do you think these lights are really accurate, or should I just change it. I have a 89 Cat 30 with a Universal M25xp.
Thanks Russ
 

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Hello all,
I am try to figure out why my oil light flickers off and on. I had a leak from my oil pan drain hose, but fixed that. Before that the oil pressure light stayed on while running engine at higher rpms. Do you think these lights are really accurate, or should I just change it. I have a 89 Cat 30 with a Universal M25xp.
Thanks Russ
First thing I would do is verify the engine oil pressure with a oil pressure test gauge. compare the results the manufacture specs then proceed.

When does the light come on? Does it come on only at idle then goes away when the rpm's are raised. Does the light flicker all the time. Personally I never really cared for idiot lights. I replace them with a mechanical gauge when ever the idiot lights give trouble.

The symptoms appear to be either a faulty sensor or chaffed wire grounding out somewhere, or you have low oil pressure.

Here is a link to your wiring diagram.Wiring Diagram
 

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Discussion Starter #3
Thanks for the help,
The light comes on at different times. Sometimes its on at high rpms and other times on low rpms. I think I will try to hook a guage up and forget the idiot light
 

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The fact of something being simple does not force it to be idiotic. As a matter of fact the simplest things are often the most functional and reliable. (think of tillers vs.wheels or furlers vs. hanks)

It worries me a hell of a lot more people trusting in space-age gauges and dials they dont't know how to read or use...

The oil "light" serves itself from a pressostatic switch to close an electrical cirtcuit which is normally used to turning on some sort of warning sign, although some instalations also feature an automatic shutdown to shut down the engine before lack of oil kills it for good.

I think it would be much more complicated for the simple user to have to know how to read an engine oil pressure gauge (do you know, for instance, what pressure to expect from your engine at idle, cruise and top rpm?) and understand its behaviour than just having to keep an eye out for the on/off state of a red light and/or buzzer.

The "oil light" is a very simple system used widely and for ages amongst almost anything with an engine and, as with every simple things, it doesn't break a lot and when it does it's easy and cheap to replace.

My advice is (assuming you engine oil level is ok) for you to have the lube pressure checked with a portable gauge and if the fault proves itself to be of the pressure switch have it replaced and forget it for a couple more decades.

:)

Regards from Portugal!

Pedro Cabral
 

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Brand new here and all but... In any other engine being a boat newb the first thing I would suggest is to check oil quantity per the manual (hot or cold , as level as possible etc.), then how old is the oil ,viscosity changes with use. Lots of times in older engines with deminishing pump efficiency oil pressure sensors can be cheated with just an oil change. Make sure you are using the correct viscosity for the temp and/or application also.
Is it more common when engine is hot or cold?
 

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The fact of something being simple does not force it to be idiotic. As a matter of fact the simplest things are often the most functional and reliable. (think of tillers vs.wheels or furlers vs. hanks)
Hey take it easy Pedro. In North America if you have a light for something on your dash that could or should be a gauge we call them "idiot lights" but that doesn't mean they are idiotic.

It worries me a hell of a lot more people trusting in space-age gauges and dials they dont't know how to read or use...
There is nothing space age about a mechanical oil pressure gauge. I would put more faith into something I can watch the O.P. go up and down with the rpm's than something that if it was faulty you would never know until it's way too late. Also I assume just about everyone here has enough intelligence to properly read an oil pressure gauge.
 

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Courtney the Dancer
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It sounds more like a bad connection or a faulty sender. I prefer to have both a pressure gauge and a low pressure light if possible but I only have a gauge now.
Reading a pressure gauge isn't beyond the capabilities of most people :rolleyes: . The normal oil pressure range is listed in all engine manuals.
 

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Learning the HARD way...
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Note that the Oil Pressure warning light, assuming that it conforms to ABYC, will be triggered by grounding the wire that comes out of the light. Put another way, there is 12V supplied to the light, which then goes through a NC switch (rated at 4psi) to the engine block, which should be a ground. If there is another path to ground (look for chafing of the wire, or something touching the leads at either end) the light will come on. I don't believe that ABYC has a specified color code for this wire, but if you add a gauge, the wire between the gauge and sender should be light blue.

- Ed
 

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A shop manual should also tell you how to test the switch itself. Often that's either an on-off connection or a variable resistance (most common) and you can test the sender with a multimeter. Senders do go bad, and if that happens you just throw it away and screw in a new one. A gauge is no panacea, it can malfunction too. And if the sender is bad--the gauge won't work either.
 

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A shop manual should also tell you how to test the switch itself. Often that's either an on-off connection or a variable resistance (most common) and you can test the sender with a multimeter. Senders do go bad, and if that happens you just throw it away and screw in a new one. A gauge is no panacea, it can malfunction too. And if the sender is bad--the gauge won't work either.
The type of OP gauge I was recommending has no sending unit that could fail. A Mechanical gauge has OP sent directly to the gauge itself via a plastic line and fitting where the sending unit thread into. The biggest danger is the line springing a leak. If you have a problem with a mechanical gauge it is way easier to tell and in my opinion more reliable than all other types of OP gauges.

Why not have the best of both worlds and install a T fitting and use the light and the gauge. What ever blows your skirt up.
 
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