Question about oil pressure and when it bypasses

by Aaron in 912 / 914 Technical Questions 5 years ago

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Re: Question about oil pressure and when it bypasses

by Bill Hertzel » 5 years ago

Bill Hertzel

13 1.95k 7.97k

As long as the Oil goes IN at the Bottom fitting on the cooler, all the Air will be gone 5 seconds after the thermostat opens.
Assuming the Mechanical gauge read 40 PSI during Takeoff, we will assume it is an electrical problem.

You have tried adding a ground at the Gauge.
Have you tried adding a ground at the Sender?

Bill Hertzel
Rotax 912is
North Ridgeville, OH, USA
Clicking the "Thank You" is Always Appreciated by Everyone.

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Re: Question about oil pressure and when it bypasses

by Aaron » 5 years ago

Aaron

14 129 67

Hi Bill,

Yes, added a ground at the gauge. I cut open the cover on the black wire coming g out of the guage and spiced a wire from there to the ground bus.

I also added a ground to the sender because the new remote mount was a 2 prong vdo sender.

Before all that I did like you suggested and took resistance from ground on guage and motor and it was good.

Is there a way to test the guage?
Can I open the 2 purple wires and hold a volt meter to see if it fluctuates?

As always...thank for the help!
Very frustrating!!

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Re: Question about oil pressure and when it bypasses

by Garrett Wysocki » 5 years ago

Garrett Wysocki

1 572 1.45k

How old is the gauge? Maybe to bearing that holds the needle is sticky giving erratic readings. I would the call the company that made it and they should be able to help you test it, specifically the ohm value you can check with a meter. Call UMA Toll Free: 1-800-842-5578 tech support.

The gauge works as an electrical current passes through a wire-wound coil mounted around or within the needle's pivot and produces a magnetic field that moves the needle across the calibrated scale of the gauge. How far across the scale the needle goes - what reading it gives - depends on how much current flows through the gauge. This in turn depends on the resistance of the gauge's return wire which is earthed to the engine block through the sensor.

The resistance of the sensor depends on the oil pressure. Oil enters the end of the sensor which is screwed into the engine block and pushes against a diaphragm. The diaphragm moves a wiper inside the sensor which runs up or down a blade of known resistance this blade is connected to the return wire from the gauge. The more the diaphragm moves under pressure, the further down the resistance blade the wiper moves. So the resistance of the sensor varies with oil pressure and moves the needle of the gauge accordingly.

Thank you said by: Aaron

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Re: Question about oil pressure and when it bypasses

by Garrett Wysocki » 5 years ago

Garrett Wysocki

1 572 1.45k

How old is the gauge? Maybe the bearing that holds the needle is sticky giving erratic readings. I would the call the company that made it and they should be able to help you test it, specifically the ohm value you can check with a meter. Call UMA Toll Free: 1-800-842-5578 tech support.

The gauge works as an electrical current passes through a wire-wound coil mounted around or within the needle's pivot and produces a magnetic field that moves the needle across the calibrated scale of the gauge. How far across the scale the needle goes - what reading it gives - depends on how much current flows through the gauge. This in turn depends on the resistance of the gauge's return wire which is earthed to the engine block through the sensor.

The resistance of the sensor depends on the oil pressure. Oil enters the end of the sensor which is screwed into the engine block and pushes against a diaphragm. The diaphragm moves a wiper inside the sensor which runs up or down a blade of known resistance this blade is connected to the return wire from the gauge. The more the diaphragm moves under pressure, the further down the resistance blade the wiper moves. So the resistance of the sensor varies with oil pressure and moves the needle of the gauge accordingly.

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Re: Question about oil pressure and when it bypasses

by Aaron » 5 years ago

Aaron

14 129 67

Good thinking...
I will call the company tomorrow morning.

Thx Garret

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