REFLECTOR: Oil Pressure

[Scott Derrick]

I think you have a bad connection somewhere between your battery and
your bus.  This could be on the ground bus or +voltage bus. One or more
of your connections has a high resistance, high being relative.  When
current starts flowing, some of the current is being turned into heat
and your seeing this on the buss as a voltage drop.

You can use voltage drop or resistance measuring to locate the offending
connection.  Set your digital ohm meter to resistance and measure across
each connection, start at the battery on the ground side,  battery to
battery connector, battery connector at battery to battery connector at
buss(battery cable), battery connector  at buss to buss, etc...   You
should see a resistance of less than 0.01 ohms at each connector.

Do the same for the + side.

Also some oil pressure sensors must be grounded, does yours require
this?  Is the sensor case properly grounded?

A bond resistance meter is what should really be used, but I've never
seen one except on the assembly line at Rockwell, Lockheed or other
aircraft manufacturing plants.

Scott

John Dibble wrote:
> At this point I'm pretty sure I do not have an oil pressure problem.  On the return from
> OSH, my observant copilot noticed that every time I turned a knob the pressure reading
> changed.  So I turned off my radio and the pressure went up 6 psi.  Then I turned off the
> transponder and the pressure went up another 6 psi, making it 51 psig which I am happy
> with.  I checked the voltage drop across the relay and it is 0.  I checked the voltage
> drop between my RMI monitor ground and another ground.  I varied from 0-0.02 v as I turned
> on a few things.  The monitor power voltage decreased from 12.6 by 0.1 volt each time I
> trurned on something.  I figure that's just the battery voltage going down with increased
> load.  What do I need to be looking at?
>
> John
>
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