Engine Alarms

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BrianCullinan

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Hi guys,
I have twin Volvo Penta diesels and the starboard engine alarm (I assume this is oil pressure - correct? At least it comes on when I turn on or off the ignition) is very intermittent - mostly it doesn't come on at all. I've replaced the siren unit (needed to be done anyway), but no improvement. I've no idea where to look for the sender unit (whatever gizmo causes the siren to go off) - if I could find that, at least I'd know if the wiring has to be chased. Any help? Many thanks as always.
 
Hi BDC,
on my boat, the engine alarms come on for both high engine temperature and low oil pressure. I think it may depend on the engines and the installation as to how yours are wired.

When you say that they come on when you turn on or off your ignition, I'm not sure what you mean as when the ignition is off they shouldn't be sounding. The way they should work is that when you turn on the ignition (without actually starting the engines), they should sound for low oil pressure (as you haven't yet started them). Once up and running, the alarms should cease as you should (hopefully!) have enough oil pressure.

You can think of them as being like an auible equivalent of the oil pressure light in your car, (with the added benefit they are likely also wired to sound in case of an overheat).

If they're only occaisionally sounding when you switch the ignition on, it's possible that you have a faulty oil pressure sender or a poor contact.

Please let me know if this helps. Depending on which model engines you have (?) either I (or someone else) will be able to point you to the sender units as needed.

Cheers,
Paul
 
But that's only ONE light-and-noise, for oil pressure. I have another similar in the alternator charging circuit. And I've fitted two more (from Halyard Marine) for cooling water flow and exhaust temperature.

Just got back from Cherbourg and not a squeek TG!

CJH
Perkins 6.354
 
Thanks Paul,
You're right about the ignition - alarm sounds when I turn on and then quickly turns off as engine starts up - at least on the port engine; alrm turns on again when I stop the engine and until I turn off the ignition.
Engines are Volvo Penta TAMD41s. If anyone can help me locate the oil pressure sender I can then check it against the port engine and start to chase the wiring - given the state of the wiring in the boat I wouldn't be surprised about a bad contact somewhere.
 
Would help to know which engines you have, I guess they are 40 somethings, in which case the alarm has 3 functions, oil,temp, and charging. The oil pressure sender is on the starboard side of the block near the oil cooler with a light blue wire, and the oil pressure alarm has a white and blue wire.
Temp alarm is up on the port side of the thermostat housing with a white and brown wire.
The charging is a brown wire and goes to terminal 61 on the back of the alternator.
Most Volvos need to be revved up over 1500rpm after starting to wake the alternator up and get it charging, otherwise the no charge light and alarm comes on.
 
Hi BDC,
I'm more familar with the 40's than the 41's, but you may find this information useful - I just want to stress that the wiring may not be identical the 40's (for example the 40 has a separate oil pressure switch for the alarm and a sender for the guage, both mounted vertically on the starboard side - I don't know whether that's the case for the 41 or if it's a combined unit), but hopefully this will give you some ideas... this is how I diagnosed the same fault on one of my engines;


A) verifed if the pressure switch is at fault by taking the wire off the top of the unit and shorting it to earth (somewhere metal on the engine is enough). i.e. If the alarm sounds with the ignition on you know that the pressure switch is at fault since you just bypassed it.

B) If that doesn't work, a similar test can be made, this time with the temp alarm wire on the thermostat housing. If this latter test works, but the first test failed, then the problem is a wiring fault to the oil pressure switch.

C) If neither test causes the alarm to sound there is something else at fault - either in the wiring or the alarm itself.

Also, the 40's don't have a charging alarm for the alternator (at least mine dont) - it's very possible the 41s do as Spannerman describes.

I hope this is useful.

Cheers,
Paul
 
I have noted the confusion over whether this alarm covers charging, which it appears to do on your port engine.

Does the starboard engine service different battery loads, the domestic bank for instance. If there is a battery or split charge device fault this could cause what you are describing.
 
Hi Andy
I think you may be right about the different loads - but I haven't really checked this out yet.
If this was the case, what should I be looking for in terms of a fault?
Many thanks
Brian
 
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