Constant Alarm - 1988 175 Mercury

[jkering66]

Hello,

I spent the weekend reading a lot of the oil/tempature alarms here, good information. I read my Seloc manual, but I am still having problems identifying what is the temp sensor, and what do disconnect to isloate the alarm problem.

Problem: Constant solid alarm when key is turned, with cold engine. When engine is started, still cold, constant solid alarm.


Tested:

Oil tank on engine is full with oil
Disconnected the blue wire comming from oil tank cap, alarm still present

Disconnected:
Green wire going to Lubalert (alarm still present)
Purple wire going to Lubalert (alarm still present)


There are 2 wires connected directly to the engine, hard wired, by the spark plugs, I belive these are temp sensors?

Tan wire and black ground on one side
Black, (I think) on other side

Are these, hard wired wires to the engine, the tempature sensor wires that I should disconnect to test to see if the alarm stops? If the alarm does stop, would that point to a temp sensor problem, since it alarms when engine is cold.

Where are the temp sensors located so I can replace them.

Thank you.

 

[j_martin]

Re: Constant Alarm - 1988 175 Mercury

There is a 2 terminal strip in the starboard side high. Under one screw the alarms come together. The other screw would have a purple switched 12 volt supply for the oil alert module.

The alarms are a single black wire from the overtemp switch, probably black, a tan/blue from the oil alert module, and a tan/blue wire that goes to the buzzer. Grounding that circuit sounds the alarm.

The key switch supplies 12 volts to the other side of the buzzer.

Disconnect all those wires. If the alarm still sounds, there's a short in the wiring between there and the buzzer. Otherwise, connect back the switch and the oil alarm one at a time. The one that sounds the buzzer is bad.

I suggest you get a real manual with real diagrams.

hope it helps
John

 

[jkering66]

Re: Constant Alarm - 1988 175 Mercury

Thanks John,

I have a SELOC 1965 to 1989 Mercury Manual, I am having difficluty reading and understanding the electronics part.


I will try to loate the 2 termnail strip you mentioned, and perform those tests.
Thanks

 

[jkering66]

Re: Constant Alarm - 1988 175 Mercury

Read my SELOC manual last night and found this information under, FUEL:



Horn Sounds Continuously When Ignition Key Is Turned On:

Possible Cause: Faulty powerhead overheat sensor

Corrective Action:

Disconnect overheat sensor and turn ignition key to ON position.
If horn still sounds continuously, warning module is at fault.
Replace module and retest.

If horn does not sound, overheat sensor is faulty. Replace.

If horn sounds intermittently, warning module is faulty Replace.




I guess I just need to locate my overheat sensor.

Looking at the diagram I need to trace the tan/blu wire from the Lubalert to the terminal block, to the Water temp. switch.


Then perform the the disconnect testing.

 

[jkering66]

Re: Constant Alarm - 1988 175 Mercury

Thanks John,

I have posted a crude diagram that I created for my engine. I disconnected the tan, tan/blu, and black wires on the terminal you mentioned.

With all 3 wires disconnected the alarm still sounds when the key is turned on.

I have had the boat for 5 years with no alarm problems.

I guess I need to trace the wires to the alarm under the dash to see what may be bad. I need to pull the steering wheel to get a good look at the fuses under the dash also.

Does the alarm have a fuse, if the fuse is bad, would that create the constant alarm.

What are the odds the alarm is bad, would it make a constant sound.

Thanks

 

[j_martin]

Re: Constant Alarm - 1988 175 Mercury

Thanks John,

I have posted a crude diagram that I created for my engine. I disconnected the tan, tan/blu, and black wires on the terminal you mentioned.

With all 3 wires disconnected the alarm still sounds when the key is turned on.

I have had the boat for 5 years with no alarm problems.

I guess I need to trace the wires to the alarm under the dash to see what may be bad. I need to pull the steering wheel to get a good look at the fuses under the dash also.

Does the alarm have a fuse, if the fuse is bad, would that create the constant alarm.

What are the odds the alarm is bad, would it make a constant sound.

Thanks

The alarm wire is shorted to ground between the terminal block and the alarm. Might be chaffed in the control, or a mouse might have used the insulation for nest making material.

The alarm is a buzzer or piezo horn. 12 volts is supplied by the ignition. The alarm circuit grounds the negative side, sounding it. Trace it out.

hope it helps
John

 

[jkering66]

Re: Constant Alarm - 1988 175 Mercury

Thanks John, that was it.

Under the guage pannel, there was a black ground that must have heated up and one point and melted/fused with the purple wire, and they were making contact.

Cleaned up that wire stuff, now I get my beep, beep, beep, when I turn the key, it fires right up, no more constant alarm.

Thanks again.