Merc overheat warnging (The SAGA continues)

[kevinclark93]

Okay I have a couple of post trying get help on this, but now I have a little more information. I have a 95 150XL offshore mercury outboard serial OG397... The overtheat alarm constant beeeeeep is going off even with a cool engine even when the engine is not on.

I have ohm checked the temp sensor and it is GOOD. I have check the wire for a short and it is GOOD.

The temp sensor has a tan/blue wire running to a post. The oil module also has a tan blue wire running to the same post. Then from the post another tan/blue wire runs to the main connector out of the engine.

So if I remove just the temp senor wire from the post the beeeep continues, but if I remove the tan/blue wire coming from the oil module with the temp senor wire removed or not removed the beeeeep stops. The oil module tan/blue wire is going to ground and completing the circuit for some reason tripping the horn.

What I find interesting is that if I remove the oil module wire and then ground the temp senor wire the alarm sounds beeeeep, so I have no idea why the oil module is on the same post as the temp senor. Since the temp sensor works with out it.

Please help... Also the wiring diagram is not 100% correct in the book I have, where can I find one for the specific engine model and date I have. I think I have a Solec book

 

[electricjohn]

Re: Merc overheat warnging (The SAGA continues)

Both circuits (oil alert & temperature) just ground, thereby completing the alarm circuit if there is a problem. That is why they can share a terminal like you are seeing. So, from your diagnostics, you have an oil or oil alert problem.

 

[kevinclark93]

Re: Merc overheat warnging (The SAGA continues)

So does the fact that the alarm sounds when the egine is off mean that it is a faulty sensor or wiring? Or can something be broken in the oil system and set an alarm off when the engine is off?

 

[sschefer]

Re: Merc overheat warnging (The SAGA continues)

From your description, I'm guessing that your oil tank is under the cover. There is a float in the tank that may be bad and could be causing your alarm condition.

So does the fact that the alarm sounds when the egine is off mean that it is a faulty sensor or wiring? Or can something be broken in the oil system and set an alarm off when the engine is off?

Is the engine off and the key in the run or on position when this occurs? The module gets it's power from what should be the purple wire on the ignition switch. If you have constant power to the purple wire with the ignition switch in the off position you have a wiring problem you need to correct. On mine the correct module function can be noted by a short test beep when the ignition is turned from off to run.

 

[electricjohn]

Re: Merc overheat warnging (The SAGA continues)

So does the fact that the alarm sounds when the egine is off mean that it is a faulty sensor or wiring? Or can something be broken in the oil system and set an alarm off when the engine is off?

If you have an alarm condition (or faulty oil alert module), the alarm in your throttle will sound with the key in the ON position, engine running or not.

The oil alert module monitors oil levels in your oil tanks using floats and also monitors a proximetry sensor which checks to see if your oil pump is spinning (when motor is running). If the sensor or floats go bad, or if the oil alert module itself goes bad, the module grounds that tan/blue wire, thereby sounding your alarm. Of course it also sounds an alarm if any of the sensors don't like what they see too, such as low oil levels or a non spinning oil pump.

 

[kevinclark93]

Re: Merc overheat warnging (The SAGA continues)

Is the engine off and the key in the run or on position when this occurs?

Yes the engine is off and the key is in the run position when the alarm is sounding.

eletricjohn:
So my next step is to check the oil float sensor, and the proximity sensor, and all wiring for shorts. How does the proximity sensor work, can I trouble shoot it with the engine off and the the key in the on posisition. I am also assuming if the float sensor and the proximity sensor are both good then the oil module itself is bad.

The oil tank is full just in case you were wondering. It does remind me though that when I was on the water and the problem started there was a small amount of smoke in the oil reserve tank, is that normal.

Thanks for all of the info this really helps a lot. I plan on trouble shooting tonight so I will let all know how it goes.

 

[joed]

Re: Merc overheat warnging (The SAGA continues)

Not sure about that particular engine but many of the Mariners have a module between the oil tank and the horn wire. It makes the oil warning beep beep beep instead of beeeeep. It also makes the initial key on short beep test.
If this module goes bad it can give exactly what you have. The module looks like a two inch square about 1/2 inch thick chunk of epoxy with wires sticking out.

 

[kevinclark93]

Re: Merc overheat warnging (The SAGA continues)

Thanks for the reply JOED

What is the best way to trouble shoot the oil module to confirm it is bad before I spend 250 on a new one.

 

[electricjohn]

Re: Merc overheat warnging (The SAGA continues)

I only know how it works but not how to determine if it is good or bad. My 90 hp Merc does not use the oil alert module or prox sensor. I believe the wires to the oil tanks can be unpluged from the module, where you could then isolate them if they are the problem. But with the prox sensor, that sends a pulsating signal to the module when the oil pump is spinning, just like anti lock brake sensors on your care does.

 

[kevinclark93]

Re: Merc overheat warnging (The SAGA continues)

Okay guys thanks for all of your help. Last night I checked all of the wiring ans sensors coming in and out of the oil module and everything was good. From my trouble shooting I am going to assume the oil module itself is bad. After I get a new and installed I will post my results.

Again thanks for the help.

 

[joed]

Re: Merc overheat warnging (The SAGA continues)

If you disconnect all the sensor wires from the module and the beep still continues then the the module is likely bad.

 

[j_martin]

Re: Merc overheat warnging (The SAGA continues)

Coupla things happening here.

If your alarm bell returns to 12 volt, not switched by the ignition switch, then either overheat or a shorted oil module will alarm with the key off. Not necessarily bad, just different wiring.

If you get a solid beep, not intermittent when you connect the oil alert wire, the oil alert module is bad. If it were one of the sensors, it would be an incessant intermittant beep.

Oil alert and overheat each go to ground when active, and are wire-or'd under one screw at the terminal strip. (either one will sound the alarm)

hope it helps
John

 

[kevinclark93]

Re: Merc overheat warnging (The SAGA continues)

I finally got around to installing a new oil module. I picked up one on Ebay used for 17 bucks which was pretty awesome. Anyways the problem is solved, my oil module was bad and the new one works fine.

Thanks for everyones help... Saved me a couple hundred bucks

 

[JimmyRD]

Re: Merc overheat warnging (The SAGA continues)

Yes the engine is off and the key is in the run position when the alarm is sounding.

eletricjohn:
So my next step is to check the oil float sensor, and the proximity sensor, and all wiring for shorts. How does the proximity sensor work, can I trouble shoot it with the engine off and the the key in the on posisition. I am also assuming if the float sensor and the proximity sensor are both good then the oil module itself is bad.

The oil tank is full just in case you were wondering. It does remind me though that when I was on the water and the problem started there was a small amount of smoke in the oil reserve tank, is that normal.

Thanks for all of the info this really helps a lot. I plan on trouble shooting tonight so I will let all know how it goes.

On my 1997 90hp merc I just found the false low oil / overheat alarm was due to the faulty float inside the oil tank. A small circular magnet had seperated from the botom of the circular float allowing the magnet to give the sensor the false reading. The float still floats but the magnet stays on bottom of tank.
I used super glue to reattach it. Works correctly now. Time will tell id super glue is effected by the oil, but better than replacement of tank,sensor and/or module. I am amazed by the difficulty of even finding the corect parts or manuals or diagrams or information. I connot justify throwing money at the problem without finding the cause. That's why I don't take it to a repair shop unless all else fails.