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Thread: R1100RT Oil pressure light comes on in the rain / after washing the bike

  1. #1
    Registered User kz1000ken's Avatar
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    R1100RT Oil pressure light comes on in the rain / after washing the bike

    So I replaced the oil pressure sensor when the oil light came on. It fixed it for a while, but came back on in the rain. It seems to be everytime I ride a long way in hard rain it comes on. I am about to go on a hunt for bare wires, corroded connectors and other electrical issues. Any suggestions for diagnoses? Something is getting wet...
    1978 R100RS , 1983 R80RT, 1998 R1100RT, 2000 ZRX1100, 2013 FLHRC
    I don't need an intervention, I need a bigger garage.

  2. #2
    Benchwrenching PGlaves's Avatar
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    Yes. That is a single wire circuit. Simplified: power source, bulb, pressure switch, ground at the switch threads in the block. When there is insufficient oil pressure a spring holds the switch closed; there is a path to ground so the light illuminates. With sufficient oil pressure the switch is held open; no path to ground; no light.

    So moisture is providing a path to ground somewhere between the bulb and the block. It is most likely right at the connection if there is a rubber cap around the sending unit. This used to happen a lot to classic K bikes.

    If not there, then maybe the insulation is nicked where the wire is in the metal clip at the side of the engine/transmission.
    Paul Glaves - "Big Bend", Texas U.S.A
    "The greatest challenge to any thinker is stating the problem in a way that will allow a solution." - Bertrand Russell
    http://www.bigbend.net/users/glaves

  3. #3
    Registered User kz1000ken's Avatar
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    Quote Originally Posted by PGlaves View Post
    Yes. That is a single wire circuit. Simplified: power source, bulb, pressure switch, ground at the switch threads in the block. When there is insufficient oil pressure a spring holds the switch closed; there is a path to ground so the light illuminates. With sufficient oil pressure the switch is held open; no path to ground; no light.

    So moisture is providing a path to ground somewhere between the bulb and the block. It is most likely right at the connection if there is a rubber cap around the sending unit. This used to happen a lot to classic K bikes.

    If not there, then maybe the insulation is nicked where the wire is in the metal clip at the side of the engine/transmission.
    Here is the new sensor replaced. There is the bare clip end on a keyed nub. 24mm bolt type, rubber crown but the contact is bare.

    1978 R100RS , 1983 R80RT, 1998 R1100RT, 2000 ZRX1100, 2013 FLHRC
    I don't need an intervention, I need a bigger garage.

  4. #4
    MOA #24991 Pauls1150's Avatar
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    The other end of that wire goes straight up to the indicator bulb. Check that socket for moisture & debris.

    Some 1100s had their wiring harness tie-wraps cinched down too tightly - look for damaged insulation which could cause an intermittent short. Some of the harness anchors use metal bands; examine those extra closely.

  5. #5
    Left Coast Rider
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    Quote Originally Posted by kz1000ken View Post
    It seems to be everytime I ride a long way in hard rain it comes on.
    This happened to me after washing the bike last week and not riding it afterwards. Next time I started the bike, the OP light went out and then came back on at about half intensity 30 seconds later. My eyes bugged out and I immediately shut off the bike. Got off and started the bike again while watching the oil window. Oil level immediately dropped so I knew the oil pump was working. Engine wasn't making any nasty sounds. And the OP light was out, too. Then I remembered I had the same issue with a Ducati about 20 years ago (I know, you're surprised). So, I believe Mr. Glaves has nailed it, as usual. We'll see if it occurs again at which point I might dig into it further.

  6. #6
    Registered User kz1000ken's Avatar
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    Quote Originally Posted by BC1100S View Post
    This happened to me after washing the bike last week and not riding it afterwards. Next time I started the bike, the OP light went out and then came back on at about half intensity 30 seconds later. My eyes bugged out and I immediately shut off the bike. Got off and started the bike again while watching the oil window. Oil level immediately dropped so I knew the oil pump was working. Engine wasn't making any nasty sounds. And the OP light was out, too. Then I remembered I had the same issue with a Ducati about 20 years ago (I know, you're surprised). So, I believe Mr. Glaves has nailed it, as usual. We'll see if it occurs again at which point I might dig into it further.
    So Im going to pull the plastic, follow the wire from the sensor to the bulb, and if I see a break, Im going to make a new wire.
    Thanks for the tips guys, you're always a big help!
    -Ken
    1978 R100RS , 1983 R80RT, 1998 R1100RT, 2000 ZRX1100, 2013 FLHRC
    I don't need an intervention, I need a bigger garage.

  7. #7
    MOA #24991 Pauls1150's Avatar
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    Um, it really sounds like it's NOT a "break" (except possibly a break in the insulation) - it's a short or other intermittent path being created along the way. See my earlier post and reconsider...

  8. #8
    Registered User kz1000ken's Avatar
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    Electrical diagnosis starting point?

    So I thought I had it worked out, but yesterday after some rain the oil TEMPERATURE read to the top on the RID (all bars) and the bike would not start.

    1. Is there an ignition kill / automatic shutoff if the Oil Temp Sensor gets too hot?
    2. Where is water the most likely to be getting to the harness / connectors. I'm going to start taking the thing apart and looking for corroded / wet connectors and wire damage.

    After several hours it started normally. Its definately getting wet. The humidity has been so bad things are rusting in the garage, so it could be condensation too.
    1978 R100RS , 1983 R80RT, 1998 R1100RT, 2000 ZRX1100, 2013 FLHRC
    I don't need an intervention, I need a bigger garage.

  9. #9
    MOA #24991 Pauls1150's Avatar
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    The oil temp sensor does feed a signal to the computer, but I don't know if a bad (or over-temp) sensor could shut down the engine. A bad sensor definitely will make it run poorly.

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