warning horn troubleshooting

[miyates]

i have a 1997 mercury bigfoot 60 hp, we just put the motor on the boat and on the first trip out the horn has sounded it goes beep beep beep! I used the service manuals located in the sticky to troubleshoot the alarm and came up with with a bad oil sensor! however before i replace the sensor i have a question the manual states isconnect both low oil sensor leads (blue) at bullet connections.
Connect an ohmmeter between sensor leads.
There should be no continuity through sensor. If continuity
exists, sensor is faulty
why would there be continuity to me that would say that the sensor is good if it is getting a current? which mine is getting a current when i disconnected it and hook it up to the meter?

 

[Texasmark]

Re: warning horn troubleshooting

Don't quote me on this as either I am right or wrong, no middle ground. I think I have read enough about it that my answer is reliable. I have a 2002 90 hp. and a service manual (1997 series) to support my answer, plus a significant education/experience in marine products and electronics.

The oil tank has a float connected to a switch and I think I read that it is a magnetic connection as there is no physical connection between the oil float and the external wiring.

When the float drops to a predetermined (low) level the magnetic switch closes causing you to have a short to ground and an alarm condition.

The easiest way to sense something is to sense it to ground. So if a low oil condition exists, the switch will close and the ground will be sent to the control module telling it that the oil tank is low on oil and the intermittent beep will be transmitted. The control module sends out an intermittent beep to distinguish between low oil and engine over temp conditions.

This is analogous to the over temp sensor that upon overheating closes putting a ground on the engine over temp line to the control module and it gives you a solid beep.............

So, in attempting to answer your question, one has to ask the question, where is the oil level when you make the measurement described in the manual. To answer that one has to assume the lead not connected to the control module is at ground potential and when the oil becomes low enough, the magnetic switch in the tank shorts out the input-output circuit to the control module telling it to send out the intermittent beep indicating that the oil supply is low. These circuits are open/closed sort of things so one should be able to detect the desired condition on a 200 ohm or less scale.

Make sense?

HTH

Mark

 

[miyates]

Re: warning horn troubleshooting

Makes since to me thanks for your time ! Since the tank is topped off I'm guessing the floats stuck down making the connection !

 

[CharlieB]

Re: warning horn troubleshooting

Adhesive failure, the magnet fell off the bottom of the float.

Since it is next to impossible to repair, order a new tank.

 

[jim765]

Re: warning horn troubleshooting

mine was stuck, new tank about 80.00 cannot replace just switch.