Volvo 2003 - oil pressure alarm

[kevrdale]

Hi, first ever post here - be kind
Our Volvo 2003 is 25-plus years old and has had a fair bit of use. We are getting a low oil pressure alarm after around an hour of motoring at 'sensible' speed. It happens when we throttle back approaching harbour, raising the revs a little silences the alarm. I have...
1. Checked the oil level - up to the top mark and no more.
2. Smelled the oil on the dipstick to check if contaminated and thinned by diesel - it isn't.
Proposed next step is to remove the sender and screw in a 'proper' gauge to check the actual pressure, cold then hot. This is where the problems start - how on earth to remove the oil pressure switch given it's 'snug' placement behind pipes, etc.? I'd welcome any advice on achieving that.
Second question: ours has a sail drive so the sender is a two-wire isolated type. If it's faulty it will need replacing but the Volvo part is around £100 - any recommendations on sources for a compatible replacement? Also, any thoughts on sourcing a combined low pressure switch and a gauge sender, bearing in mind that it needs to be an isolated type? I guess we could also create a 'T' fitting and use individual devices - has anybody done that?
I'm aware there's a certain amount of crossing fingers and hoping that the issue is not with the oil pump itself - I'd rather be sailing than dismantling an engine and the price of new pump parts looks astronomical. Again, any thoughts on stripping and replacing the pump would be appreciated.
Thanks

 

[kevrdale]

Ok, turns out a 30mm ring spanner wielded carefully does the trick and gets the pressure switch out. A gauge showed the pressure was within limits, even though the engine is knocking 30 years old. Whilst warming the engine up to check hot oil pressure the alarm sounded. Bizarrely the warning light suggested it was the oil pressure switch. Given that I had the disconnected switch in my hand, it was unlikely to be a real low oil pressure warning... So, it looks like the issue lies in the engine control/alarm panel. I'm much more comfortable with electrical/electronic issues than mechanical ones so I'm happy with the new puzzle to solve.
Take care

 

[LONG_KEELER]

Could it be the water temperature alarm ?

Overheating is common to these engines - but it is an easy non monetary fix .

 

[kevrdale]

Hi, thanks for the response. It's possible but there was no visible indicator on the panel and the engine was just on the warm side of hot - it had only been running at moderate revs for 5 mins before an alarm sounded when we were testing. The evidence seems to point to some sort of glitch on the panel, possibly within the amorphous 'black box' that house the bits of circuitry that drive the alarm indicators. I've looked at the wiring behind the panel and, despite it being in a dry locker, there's a lot of corrosion on spade terminals. Also I can't disconnect the alarm indicator black box because the the internal parts of the connector appear to have corroded together. I'm currently thinking of making a simple circuit board to mimic the function of that box. I'd wondered about temperature, but the initial fault was silenced by raising the revs slightly so I thought maybe not on the basis that that action wouldn't have altered things very quickly.
Thanks, enjoy the weather

 

[kevrdale]

Just in case anyone has been reading this short thread... I cut out the 9-way connector that appeared to be corroded inside. It joins the 'alarm box' to the loom and panel wiring. The cut wires were rejoined using standard automotive bullet connectors then liberally coated in silicone grease to prevent future corrosion. All now appears working ok, I even have my alarm test function back. After running for a while in our berth and a couple of trips out, everything seems back to normal.