Dual station electric oil pressure gauges read low and other issues

Discussion in 'OnBoard Electronics & Controls' started by sdowney717, May 13, 2015.

  1. sdowney717
    Joined: Nov 2010
    Posts: 1,175
    Likes: 85, Points: 58, Legacy Rep: 274
    Location: Newport News VA

    sdowney717 Senior Member

    I notice when I turn the key to on, the oil gauges move up to read maybe 10 psi?, without the engine running.

    That is both engines do the same thing with both gauges. And I also have upper helm gauges, so they are dual station.

    I also have mechanical gauges on the engines and they read normal, about 10 to 15 lbs higher throughout the rpm range.
    I checked the sender ohms, and it reads 120 ohms with engines off, so they are dual station senders.

    I swapped in a new gauge and it responds like the old gauge.

    Do your oil pressure gauges move when you turn on the ignition switch?

    The needles bump up when I turn on the key, from what seems to be zero to the next white line which seems to be 10 psi. These are SW gauges.

    I was thinking to use a 120 ohm resistor to check for 'zero' psi on the gauge and 15 ohm to check for 80 psi.
    single station senders are 240 for zero, 33 for 80 psi, dual are half that ohms. so 120 to 16.

    I have lived with this for a very long time. Any ideas?
  2. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    There are two types, current measuring and bridge. The ones that measure current need a voltage regulator (usually 8-9 volts). My guess is that these are the types you have and the voltage regulator is defective or has lost its ground connection.
    The needle rests below zero en should bump to zero when the power is switched on.
  3. sdowney717
    Joined: Nov 2010
    Posts: 1,175
    Likes: 85, Points: 58, Legacy Rep: 274
    Location: Newport News VA

    sdowney717 Senior Member

    Hi, thanks. I looked more closely at the gauge and the needle does bump up to the first white line, which is zero. When I first thought about it, that mark seemed like 10psi, but it is zero.

    The gauges are SW and have dual station senders. They look like this

    Mine are the marine versions so have brass casings. A previous owner replaced one with a non marine steel version and it lasted about 20 years before rusting to death. I recently replaced it with a new Ebay Teleflex as it was cheap.

    The lower helm SW gauges are not as deep and use an external under dash light bulb, they have a window in their side.

    When I find the time, I will rig up some resistors to see how the gauges respond. The dual station senders range is 120 ohms for zero psi to 15 ohms for 80 psi.
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