Mercruiser Alarm Warning System does not come on when turning the key

[alexvelarde]

Please help! My Mercruiser Alarm Warning buzzer does not come on when turning the key.
I have a 2006 Bayliner with a Mercruiser 5.0L (Serial # 0W622338)

Here's a few things I've tried:
1. I have replaced the buzzer and hooked it up to the battery and it works.
2. I used my multimeter to test the purple wire (power) and tan/blue wire (ground) that hook onto the buzzer and found out I was not getting enough voltage.
3. If I hook up the purple wire (power) and a different ground wire onto the buzzer it works which makes me think I have a problem with my tan/blue (ground) wire.
4. I tested the continuity on the tan/blue (ground) wire and it passed

Any ideas of what I could do next would be greatly appreciated? Thanks!

 

[Fun Times]

Hi there, have you tried connecting the two black wires going to the Gear Lube Monitor Reservoir together with the key on to see if the waning horn will sound?

Being a carbureted engine, 3 things turn the waning horn on, overheat, low oil pressure and low gear lube.

With the key on, be sure to wiggle the main wiring cannon plug at the engine to see if you can get the horn to sound.

Normally when you turn the key on, engine off, the horn is sounding due to no oil PSI. The horn turns off once the oil switch sees 4-6 PSI range. If the switch is defective and internally showing PSI (< you won't see psi on the oil gauge) even with the engine off, it wouldn't/shouldn't be sounding the horn and quite possibly the fuel pump may also be running but very hard to hear that design fuel pump unless you're down there listening and feeling for it.
Try lightly tapping on the oil switch down by the original oil filter location. Oil switch is merc part number 87-864252. http://www.bing.com/images/search?q=...52&FORM=HDRSC2
From MERCRUISER HORN WARNING SYSTEMS - ARI, Inc.

1995?Current 3.0L Alpha, 4.3L Alpha/Bravo, 350 MAG, 5.0L Alpha/ Bravo, 5.7 Alpha/Bravo Carbureted Engines Including TKS:
Solid horn on key on, but goes off when oil pressure switch sees 6 PSI on start up.
Normal test horn

 

[alexvelarde]

Thank you so much! Great advice!
Things I will try:
1. I will connect the two black wires going to the Gear Lube to see if the warning horn will sound
2. Wiggle the main wiring cannon plug at engine with key on
3. I will tap on the oil switch.
(Since I got the boat 4 years ago, the alarm warning system has always stayed on with the key on/engine off. The oil gauge/needle does move a little when turning the key on and it moves even more when engine is started. So, could it be the oil switch if the oil gauge/needle is moving a little when key is on and even more when engine is started?

Thank you for your help!!!

 

[Bt Doctur]

(Since I got the boat 4 years ago, the alarm warning system has always stayed on with the key on/engine off
This is the normal operating condition

The oil gauge/needle does move a little when turning the key on and it moves even more when engine is started.
Again , perfectly normal condition. gauge is reading the engine oil pressure

So, could it be the oil switch if the oil gauge/needle is moving a little when key is on and even more when engine is started?
No.

There are 2 systems here. the oil sender shows the oil pressure and the low oil switch works the alarm
There are 2 temperature circuits. one work the gauge to show engine temperature, the other sounds an alarm if there is a overheat condition.

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[alexvelarde]

Pardon my ignorance Bt Doctur... Any suggestions on what I should check next?

 

[thumpar]

Has anything been worked on/replaced about the time the fault came about?

 

[alexvelarde]

No, nothing had been changed or repaired.

 

[Bt Doctur]

the tan/blue wire will sound the alarm when it becomes grounded.
starting from the panel, does the alarm sound when the wire is grounded at the dash? Y= grounding system good, N= bad/poor ground
Does the alarm sound when you ground the tan/blue at the engine ground? y= ground good, N= ground bad
Does the alarm sound when you ground the tan/blue at the neg battery ground? Y or N?
Does the alarm sound when you ground the tan/blue at the therm housing switch? Y or N
Does the alarm sound when you ground the tan/blue at the oil pressure switch Y or N

 

[alexvelarde]

Thank you guys! It was the oil switch. I unhooked the wire that goes to it and grounded it and the alarm came on.

 

[Fun Times]

You going to order a new oil switch or already tried a new one?

 

[alexvelarde]

I just bought one...why? do you sell them?

 

[Fun Times]

I just bought one...why? do you sell them?

No I personally don't and I don't believe iboats does either. I was just curious due to you mentioned you tested the wiring and the horn sounded. Just wanted to "confirm" if you had already bought and installed a new switch and the horn came back on like normal.

 

[alexvelarde]

I just grounded the wire that goes to the oil pressure switch and the alarm came on. Once I install the new oil switch, I'll let you know.

 

[thumpar]

Make sure when you install it not to use anything that would prevent it from grounding the switch like teflon tape.

 

[alexvelarde]

Thank you! The oil switch just came in. I appreciate the advice thumpar! I'll keep you guys posted!

 

[alexvelarde]

Installed the oil switch and it works! Thank you guys!!!