Oil warning light

[baltimorenick]

My oil warning light was showing the other day on the highway. It would light up for a little while, then turn off, then light up again with no discernable pattern or cause/effect due to riding conditions (i.e. gear/rpm/speed). Today it hasn't showed up at all. It is worth mentioning at this point that the oil is filled to the proper amount, has a new filter, etc. Is it reasonable to assume that I was getting a warning light due to using 20W40 oil at below 40F temperatures? The oil was simply too viscuous to hit the pressure switch consistently? Since it is much warmer today, the oil reached proper operating temperature and flowed correctly? This is the assumption I am making now. Also, how likely is it that permanent damage occurred while the pressure was too low? Thanks for your input guys.

[bikerphil]

Nine times out of ten, the false warning from the oil light has nothing to do with loss of pressure or a bad sensor. The 79 Special (only) has a "light checker unit" which illuminates the oil light if the tail/brake light bulb burns out. Check the connections on the LCU under the left side cover. Also check your tail/brake light bulb.

[motoman]

My oil warning light was showing the other day on the highway. It would light up for a little while, then turn off, then light up again with no discernable pattern or cause/effect due to riding conditions (i.e. gear/rpm/speed). Today it hasn't showed up at all. It is worth mentioning at this point that the oil is filled to the proper amount, has a new filter, etc. Is it reasonable to assume that I was getting a warning light due to using 20W40 oil at below 40F temperatures? The oil was simply too viscuous to hit the pressure switch consistently? Since it is much warmer today, the oil reached proper operating temperature and flowed correctly? This is the assumption I am making now. Also, how likely is it that permanent damage occurred while the pressure was too low? Thanks for your input guys.

What bikerphil stated would be a good start. Don't think viscosity has anything to do with it. Heck, 30yrs. ago before I had a garage, used to cover mine with blankets with a heat lamp under it. At -20 to-25degrees sometimes it would start and sometimes not. Either way still run 20-50w and was never an issue, cept for the occassional slow turning over. Now knowing what I do, Im sure the petcock diaphrams were too cold to react to any vacuum created while cranking. Likely would of started more regularly if I'd flipped them to prime. IMO, once running and warmed up, outside temp has no effect on viscosity as that motor IS hot, even when outside temps are colder.

[ddragon63]

I rode mine to work yesterday. it was 33 outside and I run 20w-50 with 10oz of Lucas stabilizer in it... I've never had that problem. check the connection on your pressure sensor too along with the LCU. I had to remove my LCU to make all my lights work the way I wanted on mine so the oil switch is the only circuit on that bulb, I've fired my bike below freezing in the garage many times and the light goes off as soon as the bike fires up even with the thick mix I run. So I don't think its your viscosity...

[baltimorenick]

Thanks for the good info guys. Both filaments of the tail/brake light are working so there must be a crappy connection somewhere. I will wiggle some connectors around tomorrow to see if I can get the idiot light to come on again. Also, I just want to say that this forum is great!

[jetmechmarty]

In recent months I had to fix poor tail light connections on two XS bikes. It isn't uncommon, apparently.

[bikerphil]

With the bike running in neutral, try twisting the loom that goes into the LCU itself and look to see if the light flickers. That's how I fixed mine 6 yrs. ago, just twisted the wires and it is working correctly to this day. YMMV
If you want to bypass the unit altogether for further testing, just unplug it and jump the blu and blu/yel terminals in the harness connector.

Here's what the LCU looks like...

[Jerry]

I had a similar problem with a Yamaha 400. Cleaned the top of the sensor and that fixed it. So much dirt/garbage on it the signal was 'bleeding" between the contacts, giving a false reading.

[airborneXS]

mine does the smae thing...ive learned to just ignore the light all together...

[BA80]

mine does the smae thing...ive learned to just ignore the light all together...

I hear what your sayin' Wolf Man but you might want to fix that because if that oil light is working right it just might save your engine some day. IMO

[natemoen]

I hear what your sayin' Wolf Man but you might want to fix that because if that oil light is working right it just might save your engine some day. IMO

+1, That light serves a real purpose other than that stupid burnt out light warning.

[conquest87tsi]

Light

I need some clarification,
So what exactly is jumping the blue and blue yellow wire do? With the LCU disconnected, well the oil pressure switch still illuminate the light?

The reason I am confused is that everyone says to remove the LCU and jump the blue wires. Well my light is off with them removed anyway.

[bikerphil]

When you bypass the LCU, the oil light will not illuminate if you have a burned out tail light bulb, but it will still function normally when there is no oil pressure at the engine sensor. These units commonly fail so your options would be to try to twist/wiggle the wires coming from the unit to see if that corrects the problem, or, replace the unit, or, bypass the unit. To test, the oil light should come on with the key on, but turn off when the engine starts.

[conquest87tsi]

Lcu

Ok,
So as I stated before, the problem started when I installed LED tail lights. However, I just noticed that when I replaced my starter cover the pressure sender wire was pinched a bit. I removed the connector to see if the light would stay off, and it did, but why moving it around the light would blink, shorting somewhere.

I had an extra wire from my parts bike and threw it on. (Not exactly that easy without removing the carbs). Now the light turns off with the bike running and the LCU removed.

So, must the LCU be hooked up for the Pressure switch to work? OR Do I just have to jump the blue wires and not use the LCU? I'm just not sure what everyone means by "bypassing" it.

With the LCU removed, the pressure switch will not work unless the blue wires are jumped? Is that correct? If so, why does the OIL light come on when the pressure switch wire is connected, and doesn't when it isn't?

It seems to be working regardless of the LCU. Or isn't it actually checking it?

[conquest87tsi]

Lcu

Just to clarify, I DO want to bypass the LCU. Those LED's will probably outlive me anyway.