Bonneville America Forums Forums Technical Forums General Tech false oil pressure indication?

I have an '05 with 3500 miles. It had its first service in May at 500 miles, so I've put 3000 miles on in the couple months since then.

A couple nights ago, my low oil pressure indicator came on while I was riding. I got home, and the oil level was in the bottom half of the glass, but still visible. I haven't seen any leaks or signs of burning. I topped the level off just a bit anyway.

Since then the oil pressure indicator will come go off when I start the bike, but as it warms up it comes on again and stays on.

What could be causing this? Is it a false indication? Is it possible for the oil pressure to be low even though the level is fine?

I am not sure its false. Are you lucky enough to still have that bike under 2 years from its first sale? If so, dealer time. Get those oil pumps checked now to ensure its a false reading. You don't have to be out of oil for the light to come on it is also for high or low pressure.

The light indicates oil pressure, not oil level in the sump. Although low oil is the most common cause for low pressure you -could- have a problem with one of the oil pumps too.

This exact thing happened to me about 2 years ago when the bike was still under warranty. I put it on a trailer and took it to the dealer, just in case. Turned out to be a problem with either the sender or the wiring loom for the sender. Mechanic wasn't sure which, so he replaced both. After replacing the loom he discovered a crack in the rubber boot protecting the sender which had allowed moisture into it, so that'd be your first place to check.

same happened to Wendy that's what prompted me to fabricate our oil pressure gauges. She had the light come on after washing it from the same type of cracked boot as Sandman
mentioned.

>After replacing the loom he discovered a crack in the rubber boot protecting the sender

>same happened to Wendy

Mine pretty well disintegrated & dealer said it's not available.
I bought a new sender, & the boot didn't come with it.
Now running sans boot.
Haven't looked for aftermarket/generic.

Matt - did you get a replacement?
Ian - did you check for sources?

Just gob some black tape or RTV on the wire. The boot is part of the complete wiring harness. I tried to get a replacement and found this out. No way am I spending $325 to get a new rubber bootie.

I had no interest in fixing the sending unit so I didn't look but it has worked fine ever since it dried out. I decided to put a gauge on with the sending unit so I had 2 indicators and if the idiot light fails again I have a gauge to look at and in addition to that if there is a drop in pressure I can see it before it drops far enough to trigger the light or cause damage.

Does the engine make any more noise than usual when light goes on? The oil pump gears are plastic.
OT- Anyone heard from Roundslide? He had bronze gears made, sold a bunch of spare parts, haven't heard from him since.

You have 3 possible causes.
1. The pressure really does drop off when the oil warms up and thins out. Might be the wrong weight oil or something like a worn oil pump or bearings causing the pressure to be low. Also, thanks to total noise limits imposed by the politicians, the oil pump is driven by a plastic gear. If this gear is worn just right, it could act like a slipping clutch, especially when the engine is warm.

2. There is a short in the wire between the indicator light and the pressure sensing switch.

3. A leak in the diaphragm in the sensor switch can cause this. Oil pressure moves the diaphragm and shuts off the warning light when you first start the engine. Oil then leaks through the hole untill the pressure on both sides is equal, the diaphragm relaxes and the warning light comes on. I had this happen on a Hudson once.

Well, the next time I went out to my bike the problem was gone. Rode all weekend with no problems. So I'm suspecting a moisture-induced short.

Thank you all!