Testing Gauges

[GILDIA]

I just measure at the VR and i get 13.9 Volts to the gauge, and i also measure the resistance from the temp sensor and i get around 200 ohms and it decreases at time pases by, but i dont get a reading at the gauge, I am going to open it and clean it

[geezer]

I'm not familiar with the testing proceedures used for these gauges and don't know what the voltage reading should be at the VR (limiter), but if you feed it a ground in place of the transmitter wire it should peg the needle. If not I would suspect the gauge itself as being at fault. That's just my guess. You need to hear from someone that is familiar with a tried and true method of testing these.

[Nissanman]

...around 200 ohms and it decreases at time pases by

That is the typical property of an NTC type sensor, Negative Temperature Coefficient.

Simply put it means that the sensor resistance to earth reduces as the temperature increases.

The attached thumbnail shows the behaviour of such a device.

Don't expect these values to be exactly those of your sensor but it is what it should do with temperature variations.

The oil pressure sensor is usually exactly the opposite.

As the the pressure increases the resistance of the sensor also increases, Positive Pressure Coefficient.

That is why unplugging the sensor wire, introducing maximum resistance to earth, results in the Oil Pressure gauge maxing out.

The typical symptom of a faulty oil pressure sensor as it deteriorates, is the wiper inside it wears an open circuit at the "normal pressure" point of the sensor resistance coil.

That causes an intermittent open circuit to be read and the gauge needle jerks and jumps about the faulty position.

Usually the only remedy is a new sensor since they are not repairable to my knowledge.

[GILDIA]

:stupid:I guess i am going to need a new gauge, I tested it with an external source (12 volt) and the gauge skoke start ti get out of the gauge :stupid:

So I made a mistake but i learned from it ...