Oil Pressure Switch vs Oil Pressure Sender

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GeoffSchultz
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Oil Pressure Switch vs Oil Pressure Sender

Post by GeoffSchultz »

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 have replaced the oil pressure switch in 2011 by accident. I had wanted to replace the sender unit but the part # is 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
BlueJacket
1997 Freedom 40/40
http://www.GeoffSchultz.org

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rvivian
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Re: Oil Pressure Switch vs Oil Pressure Sender

Post by rvivian »

Might be a small (intermittent ) electrical issue with the idiot light.
Heart's Desire
Freedom 30
Shelton, WA

carhelpguy31
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Re: Oil Pressure Switch vs Oil Pressure Sender

Post by carhelpguy31 »

If you are looking to get rid of the annoying light and alarm until you can get somewhere to fix it, you can disconnect the pressure switch as it may be shorting out. Without getting to technical, the way these usually work is voltage from the light and buzzer will be provided with a path to ground through the switch when there is no oil pressure. By disconnecting the switch it opens the circuit and you should be good to go until you can locate a new part. Senders work different as they vary the resistance of a reference voltage depending on pressure which adjusts the position of the gauge. Have a great trip, I would love to see some pictures.
Mike Russell
Bazinga!
Freedom 30/32
Cheboygan, MI.

midnightsailor
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Re: Oil Pressure Switch vs Oil Pressure Sender

Post by midnightsailor »

Sounds like a problem with the pressure switch, so relax , enjoy yourself and believe your pressure gauge. I have had to replace faulty presure switches myself, be glad you have a gauge, so many boat s just have that idiot light.
1982 Freedom 33 Cat Ketch, Hull # 53, Standard Booms, deep keel ,tall rig
An armed man is a citizen, An unarmed man is a subject. George Washington

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GeoffSchultz
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Re: Oil Pressure Switch vs Oil Pressure Sender

Post by GeoffSchultz »

Thanks for the feedback. I have limited Internet connectivity down here.

I don't believe that this is an electrical problem. I have come to trust the gauge, but I want the alarm to work if something were to fail. I still have 600 miles to go until I reach the terminus of this year's cruise and since there's very few resources to fix an engine problem down here, I don't want to risk anything.

I just pulled into Zihuatanejo and will pull the oil pressure switch today to see if there's anything mechanically wrong with it. Failing that I'll head to an AutoZone and hopefully find a switch that is usable.

Note that I publish extensive logs/photos from our travels. You can find these at http://www.GeoffSchultz.org and/or if you use FaceBook, you can also "like" my sailing page and get much more frequent updates: https://www.facebook.com/BlueJacketSailing

-- Geoff
BlueJacket
1997 Freedom 40/40
http://www.GeoffSchultz.org

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GeoffSchultz
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Re: Oil Pressure Switch vs Oil Pressure Sender

Post by 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.
BlueJacket
1997 Freedom 40/40
http://www.GeoffSchultz.org

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GeoffSchultz
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Re: Oil Pressure Switch vs Oil Pressure Sender

Post by 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...

I put the new oil pressure switch in and no change. Then I disconnected the wire and the alarm was still present. I 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
BlueJacket
1997 Freedom 40/40
http://www.GeoffSchultz.org

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