Yanmar oil alarm

[stephen_h]

Hi all,

My Yanmar 3GM30F started sounding the panel alarm (oil pressure).
I changed the oil pressure switch and started with the alarm still not stopping.
Started again straight away and all fine, no alarm. Next weekend tried again and now the alarm won't stop again.
Forgot to mention that all the lights go out even though the alarm is still on.
I don't have a pressure gauge to check the oil pressure but was going to run the engine to see it it heats up too quickly.

Not sure if it is connected but also found the raw water impeller was broken (no water at exhaust)
and some missing fins. Got to find those before I can sort the oil problem!!

 

[awol]

Hi all,

My Yanmar 3GM30F started sounding the panel alarm (oil pressure).
I changed the oil pressure switch and started with the alarm still not stopping.
Started again straight away and all fine, no alarm. Next weekend tried again and now the alarm won't stop again.
Forgot to mention that all the lights go out even though the alarm is still on.
I don't have a pressure gauge to check the oil pressure but was going to run the engine to see it it heats up too quickly.

Not sure if it is connected but also found the raw water impeller was broken (no water at exhaust)
and some missing fins. Got to find those before I can sort the oil problem!!

The oil pressure switch is a simple open/closed device. A multi-meter, even a light bulb, will show if the problem is really oil pressure - in which case I would advise against running it - or an electrical glitch elsewhere.

 

[Ammonite]

Oil pressure test kits are less than £20 on eBay if you want piece of mind. I have one of these. I'm never sure if these cheap eBay kits are worth the money but this one gave exactly the same readings as a new VDO gauge and sender. My original 25 year old VDO gauge was under reading by 15psi.
Pardon our interruption...

 

[stephen_h]

The oil pressure switch is a simple open/closed device. A multi-meter, even a light bulb, will show if the problem is really oil pressure - in which case I would advise against running it - or an electrical glitch elsewhere.

So does the pressure switch cut the power when the oil pressure is correct?
The switch is behind the fan belt so not easy to check when the engine is running but could find a way.

 

[Dellquay13]

So does the pressure switch cut the power when the oil pressure is correct?
The switch is behind the fan belt so not easy to check when the engine is running but could find a way.

Can you trace the wires from the switch and meter them at the other end away from the fan belt?

 

[Mistroma]

So does the pressure switch cut the power when the oil pressure is correct?
The switch is behind the fan belt so not easy to check when the engine is running but could find a way.

I don't have the manual to hand but it makes sense that way. The switch shorts with low pressure and opens when it increases. That makes for a very simple circuit with the light powered when engine on. More complicated to do it the other way around and I'd be surprised to find anyone designing them that way.

 

[stephen_h]

I don't have the manual to hand but it makes sense that way. The switch shorts with low pressure and opens when it increases. That makes for a very simple circuit with the light powered when engine on. More complicated to do it the other way around and I'd be surprised to find anyone designing them that way

The oil light on the panel goes out so I assume the power has been cut. Just the alarm still going so maybe electrical short somewhere.
Surprised since the wiring loom was replaced a few years ago but I guess could be wear somewhere.

 

[Mistroma]

The oil light on the panel goes out so I assume the power has been cut. Just the alarm still going so maybe electrical short somewhere.
Surprised since the wiring loom was replaced a few years ago but I guess could be wear somewhere.

You'd expect the alarm to be in-line with the light and fed power via the same sensor. Again, simpler to build that instead of an extra circuit with a second sensor. It makes sense that the alarm sounder is shorting to -ve somewhere. I'd start checking at the sounder when engine is running, rather than at the sensor. That would seem to be OK if the light is going out.