Oil Pressure Guage/Sending unit

[James Evans]

Purchased boat last year, had a mechanical oil pressure gauge. Found original gauge behind panel, purchased sierra 18-5899 sending unit and the gauge pegs 80psi as soon as the key is turned on, engine not running. No change when started, still pegged at 80. Ran wire directly from sending unit to gauge and same thing pegged at 80psi. Gauge must be bad. Found a few that look the same/identical on fleabay, and my question is are all the marine gauges run on the same ohms and/or do the VDO use another ohm scale?

I don't want to buy another gauge and it not work with the 18-5899 sending unit.
If the VDOs use another scale I need to know the correct sending unit to use with the original gauge.

Any help appreciated!

[morpheusmac]

Ohm test the wire from the sending unit to the gauge and see if it is the right wire. Sounds like the gauge may be getting a grounded signal to the gauge.


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[morpheusmac]

My oil pressure gauge is stuck at 30 psi...grounded or not running or not, no movement. I just ordered a new gauge, hopefully the sender is ok.


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[James Evans]

Gauge falls to zero as soon as I unhook it from the sender. And goes to 80 hooked up, or with a dedicated wire directly from sender to gauge, to take the factory wiring out of the loop.

[morpheusmac]

Sounds like the gauge is working fine. Are you sure the sender is putting out the correct signal for the gauge?


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[roosm]

Ohm test the wire from the sending unit to the gauge and see if it is the right wire. Sounds like the gauge may be getting a grounded signal to the gauge.


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What he said..
You should see something like 240 with engine off. 100 would be 40 psi and 30 would be 80 psi. Anything below 30 ohm would spike an 80 PSI gauge.
If you see somewhere between 100 and 60 ohm at idle the sending unit should be ok. That would roughly translate to somewhere between 40-60 psi.

[michael hunter]

Sounds like you have an automotive sender .

[James Evans]

Ended up being the gauge. Found a NOS on fleabay and popped it in and now have a working gauge.