Mercruiser 3Litre LX Warning Alarm

[Taz59]

1995 Mercruiser 3Litre LX
On my dash it says to check if warning system is working turn ignition to on and after 15 seconds horn should sound, but it does not work. how can I check Oil,Temp & low gear lube switches




Col

 

[Don S]

Re: Mercruiser 3Litre LX Warning Alarm

Before checking the switches, you need to check the alarm buzzer and see if it works. In the mid ninties, merc used timer circuits on the alarms, and they failed quite often, then Merc went back to just a straight alarm buzzer.
With the ignition switch in the run position, remove the oil pressure alarm switch and ground it, the alarm should sound. Same with the over temperature switch and gear lube reservoir. If nothing sounds, the buzzer is probably bad, or the wiring going to it.
Here is a link to the OEM service manual you can download. It has wiring diagrams and test procedures for the switches.
http://www.4shared.com/document/B3wzU5Iz/Service_Manual_13.html

 

[Taz59]

Re: Mercruiser 3Litre LX Warning Alarm

Check wiring and found that the oil pressure wire had been disconnected so reconnected still no alarm,checked alarm by putting 12v to it and its OK, On the alarm it looks like something is missing there is a plastic tube with nothing in it,not sure what type I have,on the alarm it has Delco Alarm there is only two wire going to it,should there be a time relay some where.

cheers

 

[burp]

Re: Mercruiser 3Litre LX Warning Alarm

Taz,

As Don mentioned, if you take the wire off one of the alarm sensors and ground the end of the wire to the engine block, you should have an audible alarm. If not check the alarm buzzer and wiring from the alarm sensors/switches to the alarm buzzer.

The alarm sensors/switches should ohm out as:
oil pressure alarm sensor/switch - short/zero ohms with no oil pressure, open/infinity with oil pressure
temp sensor/switch - open/infinity with normal temp, short/zero ohms with an overtemp condition
lube sensor/switch - open/infinity with a full lube level, short/zero ohms with a low lube condition

 

[Taz59]

Re: Mercruiser 3Litre LX Warning Alarm

Cheers Burp
So oil pressure switch in normally closed
Temp & lube switch normally open.
Will check this weekend

Are the switches in series or parallel

Cheers

How can I tell which one have earlier or later model

 

[burp]

Re: Mercruiser 3Litre LX Warning Alarm

Parallel circuit

 

[Don S]

Re: Mercruiser 3Litre LX Warning Alarm

Have you looked at the manual I gave you a link to? It explains exactly what they are, how to check them, and how they are wired in.

 

[Taz59]

Re: Mercruiser 3Litre LX Warning Alarm

yes downloaded manual,will check this weekend.Possible wiring fault from engine up to alarm,checked continuity from temp switch to alarm no reading.also noticed on the alarm itself its sits in a plastic housing but looks like there is something missing as there is a hole (tube) where something should fit,just wondering if this is where the timer goes ??????