Oil Pressure Light- Wire Replacement?

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Oil Pressure Light- Wire Replacement?

Postby ASLRider » Mon Oct 28, 2013 10:31 am

So yesterday my dad asked me how my bike was running, knowing I had to do some emergency repairs a few months back. I said that Erni is running great, and consequently this morning I got an oil pressure warning light on my ride to work. Damn Murphy and his stupid law.

So I immediately pulled over, having remembered Chaz's horror stories (among others) about blowing out the sight glass, spewing oil all over the road, and killing the engine entirely. All of these stories started with an oil pressure warning light.

I looked around my sight glass and oil sensor plug (both of which I replaced within the last year) for any obvious leaks, and although the engine is definitely dirty, which may show a slow leak, I didnt see anything catastrophic. I was almost to work so I finished the ride there.

My real question is, could this be a false positive? The wire that leads to my oil pressure sensor has a patch where the insulation was cut through, and I have covered it with electrical tape, but i am guessing it would be fairly easy to short this out and turn the light on. Any ideas on how I could test this theory to see if it is a false positive? If it is the wire- ideas on how to replace it? It goes all the way up the harness, I imagine to the gauge cluster. Could I splice in a piece of wire inside the housing that covers the starter motor?

If we think this is not a false positive- ideas on where else to look for a leak? I checked the oil in the sightglass and it is still up to at least the midline. I imagine I could top it off, and see if this turns the light off.... right? I have had oil leaks in the past at the sightglass, pressure sensor, and fill cap... other spots I should be looking?

I have a photo of the area but have to figure out how to get it up somewhere from my iPad... stay tuned.
-G
http://www.gerardwilliams.net
1994 R1100RS "Erni" (thanks Karl!)

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Re: Oil Pressure Light- Wire Replacement?

Postby ASLRider » Mon Oct 28, 2013 10:44 am

Photo (I hope)

Image
image by WilliamsGerard, on Flickr
-G
http://www.gerardwilliams.net
1994 R1100RS "Erni" (thanks Karl!)

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Re: Oil Pressure Light- Wire Replacement?

Postby Genen8kua » Mon Oct 28, 2013 10:57 pm

So testing your hypothesis should be pretty easy - the switch is "normally closed," which means it opens (breaks the circuit) when it senses enough oil pressure (abt 5psi) and closes (completes the circuit to ground and lights the light) when the oil pressure is low. That's why it should light when you first turn on the ignition, but quickly go out as the engine starts.

If you disconnect the wire from the oil sensor and keep it away from other metal (i.e. don't ground it), then the oil light should not light when the ignition is first turned on. Grounding the connector by touching it to exposed metal on the engine should then light the oil warning light.
If it passes the above test, then the wiring is functioning ok.

If the light stays lit regardless of whether or not the wire is attached to the sensor (or grounded), then there's likely a short somewhere, and the old repair wouldn't be a bad place to look, especially that spot in the picture where the wire is fixed to the engine with a metal clip. Before you undertake the systematic approach above, you might just unclip the wire, keep it away from the case, and see if that cures the problem.

If the circuit is fine, then you get to figure out if the problem is the sensor (might just want to swap it out with a replacement like http://www.euromotoelectrics.com/Oil-Pressure-Switch-for-BMW-R-Airhead-Oilhead-K-p/ops-414.htm ) or a more serious low oil pressure problem. An oil level that's just a little bit low shouldn't cause the oil pressure warning to light.

I hope it's the circuit or the sensor, as even a short trip with insufficient oil pressure could cause real damage.
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