1993 Mercury 115 Alarm Control Unite

[Packard1807]

I have a 1993 Mercury 115 hp outboard motor that has the alarm sounding continuously. I have replaced the overheat sending unit in the head, and the alarm is still on. Is there an alarm control unit and if so, where is it located? Any other ideas of what the problem might be? Thanks!

 

[skytracker]

The alarm module should be on the starboard side right behind the main electrical connector coming in. The temp sensor wiring you will need to take off one at a time from the terminal block just aft of the module to isolate which one it is. You could also have a faulty horn. Disconnect the Tan/ blue wire from the block and see if it goes away. That comes from the main connector. If it does one of the sensors is still grounded and problem should be on the engine. Still goes off? The horn or wires to it.

 

[Packard1807]

Thanks, Skytracker. The alarm module you refer to on the starboard side, I sometimes see it referred to as the "oil warning alarm control unit" and then just the "alarm control unit". I replaced it, and the alarm is still sounding continuously. Is there another alarm control unit or is that the only one?

I will follow your recommended process for further diagnosing the problem. Thanks, again!

 

[racerone]

Maybe the buzzer is defective ?

 

[MercGuy]

It is possible that the magnet on the float in your oil reservoir has separated and fallen to the bottom of the tank. That would close the oil alarm switch and cause a constant beep from your warning buzzer.

 

[Packard1807]

I disconnected the light blue wire from the alarm control unit that go to the oil float sensor. The horn was still sounding continuously. I now believe that the used alarm control unit I bought is also defective.