Oil Pressure Switch vs Oil Pressure Sender

[zeehag]

geoff--autozone is on the main road that goes between ixtapa and zihuat. my repairman is due back here any day now, and will be more than glad to help if you are where i am.
i remembered your boat name at 0300.....

 

[Rick486]

Last night we were on a 190 nm passage from Manzanillo, Mexico to Ixtapa. Just as I was about to come on the 3 AM shift, the oil low pressure alarm went off. I raced up and looked at the panel and I could see that the pressure gauge was reading correctly. When I changed the engine RPMs, the pressure did what I expected it to do. We had a little wind, so we put up the sails and sailed at 2-3 kts. I checked the engine oil levels and they were fine.

Amazingly we had very limited Internet access and I texted Dave Balfour, who's a great friend and was responsible for commissioning BlueJacket when he worked at Freedom, and described the issue. He said to believe the pressure gauge and not the idiot light. What wind we had finally died and I fired the motor back up. The light was on, then went off as expected, and then a minute or so later flickered on. We ran with it on for hours and then it suddenly went out.

I replaced the oil pressure switch in 2011 by accident. I had wanted to replace the sender unit but the part # in the manual was wrong. Unfortunately I didn't keep the old switch.

This is on a Yanmar 3JH2-TE. Note that the oil pressure sender and the pressure switch take their readings from basically the exact same location.

Anyhow, the area where we're at is basically devoid of marine services and we have 600 miles to go along some pretty desolate coast. I might be able to find a diesel mechanic in Acapulco, but I'm not sure. Scary thought!

Does anyone have any experience with something similar?

-- Geoff

Recommend you check carefully around the sender locations to be sure there is not an oil leak on the sender. I once lost the entire engine full of oil out the oil pressure sender on a long motoring passage. I didn't suspect a thing until the oil pressure alarm sounded and I rushed below to see all that oil in the bilge. When the sender fails this way it opens up a 40 psi drain and it doesn't take long to empty the engine sump. This was a perkins 4-108. No damage to the engine but a big mess to clean up.

 

[geoffschultz]

I arrived in Zihuatanejo yesterday and am anchored next to Zeehag's boat, Solitary Bird.
Today I'll pull the oil switch and see if there's anything mechanically wrong with it. Failing that, I'll make my way to the AutoZone and see what they have for parts to replace the switch with.

I have no oil leaks and the oil level is full. I don't believe that this is an electrical issue because of the way that it behaves. A new switch will require a bit of jury rigging since the old one only has a single wire and completes the circuit path to ground via its case and all of the others that I've seen have 2+ wires wire connectors, but that's not a big problem. I'll let you know how it goes.

Once again, thanks for the feedback!

-- Geoff

 

[Charles Erwin]

One wire only on your sender

 

[geoffschultz]

One wire only on your sender

The spare that I have for my generator has 3 wires. common, nc and no

-- Geoff

 

[geoffschultz]

Today I discovered that you need a 15/16" socket to get the oil pressure switch out. I had 7/8 and 1" deep sockets and no one in the anchorage had a 15/16". As a result I couldn't get the part out before heading to AutoZone. I managed to find both a normal and deep 15/16" socket & I bought both because I wasn't sure that a normal socket would be deep enough to fit over the screw terminal.

About an hour after leaving I made it AutoZone only to find that they don't have the part, but can get it in 7-9 days. Yeah...And since I didn't have the part, I couldn't check the threads of the other ones that appeared that they would fit.

So tomorrow I guess that I'll hike another hour each way to the AutoZone to see if I can find a switch that might work. Ah, this is *real* cruising!

-- Geoff

P.S. The standard socket works.

 

[geoffschultz]

I also just figured out that the spare oil pressure switch that I have for my generator is NPT and the Yanmar uses BSPT. I don't think that I have space for an adapter.

-- Geoff

 

[geoffschultz]

Today I hiked back to the AutoZone in Zuatanejo with my old oil pressure switch to use as a model and amazingly they came up with a OP8000 which cross references to a PS100, which I tried to buy from them yesterday. Argh...it's only an hour walk each way...

Put the new oil pressure switch in and no change. Disconnected the wire and the alarm was still present. Kicked myself in the head for not testing that earlier, but I was pretty convinced that it wasn't a wiring issue due to the way that it flickered and came on steady.

I then found a an unused signal wire (for my non-existent sail drive) and used that wire for the oil pressure switch signal and all is fine now.

Thanks once again for all of the suggestions and help!

-- Geoff

 

[kloudie1]

Ahh.. Glad ya found the problem!