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Hello, My name is ***** ***** Im a qualified Heavy Equipment Mechanic. I will do my best to explain to you the different types of sensors used for fuel sending units.Older fuel sending units use an electrical sensor called a Rheostat. This is a 2 wire sensor that uses a variable resistor to drop a portion of the voltage supplied by the battery. One wire has a supply, and the other, a groundNewer equipment with fuel sending units use a 3 wire sensor. One wire is called the "supply" which supplies a source voltage of 5v from a computer. The second one is called the "signal" which measures a signal from the 5v depending on the position of the sensor. The third one is a "return" or ground, which is a negative ground supplied by the computer as well.A 2 wire sensor is much easier to test, using a standard multimeter or ohm meter. A 3 wire sensor is best to test and observe using a scan tool as you need a 5v supply, a signal, and a ground applied to the sensor.I hope this answer helps you understand the differences in some fuel sending units, compared to others and why some are easy to test, and others aren't. If you have any other questions, I would be happy to help! If you could leave me a feedback of the service I supplied today, that would be greatly appreciated!Derek
With an analog sensor, the direction of current flow is not relavent. With a digital 3 wire sensor, some are ground controlled.The reason you are not able to test the 3 wire sensor is no becase of the ability to control the ground, but because of the nature of the sensor itself. The best way to test these sensors is through the use of a scan tool as the computer supplies the correct voltage to the sensor to be operated.Does this answer your questions?
Ok, I understand what you are working on now.If you are working on a 2 wire sensor, one wire will have an input voltage, and one wire is a ground. What you need to do is check your input for voltage. Attach you + probe to the input, and your - probe to the battery ground. If you read voltage doing this test, but have no voltage when connecting your - probe to the sensor ground, and your wire to your ground is good, your fuel sending unit is faulty.
Do you have any voltage on the - side of the sensor to ground? Why are you testing it if it works properly, I don't understand your problem?
If you ready my my previous post you would see I am trying to help you diagnose the problem. I am not a mind reader, and don't have all the information you have available to me to understand what you are asking. I had no idea what tracker you were refering to, nor what is was for. Please read my posts carefully and answer thoroughly so that I can help you to the best of my ability.As I asked previously, is there a positive voltage from the ground side of the sensor? (+ probe on ground side of sensor, - probe on negative of battery)
So if you have 12v's on the input, and .2-.6 on the output. The sensor is block 11.4-11.8v depending on the level of the fuel float.
It completely depends on the manufacturer. Different manufacturers supply a different amount of voltage to the sensor. If the sending unit is operating normally, and those are the voltage readings you are getting, I would take them as correct.
This is quite an unuasual and very specific question that I can't help you answer. I will see if any other expert has an answer.
Hi my name is***** will try to help further. There are so many different style fuel level sensors as you know each constructed differently and spec'd differently per manufacturer. On this particular sensor run an OHM meter on the ground side and monitor your resistance to ground. Also with power disconnected probe the two terminals while moving the sensor float and record your resistance values. If this style is not compatible with your monitoring system then install a separate sender that is. Click on this link for an option.
Let me know
Installing a fuel level sensor that has accurate readings from multiple sensing points is important. Some sending units will not give you this unfortunately. The link I posted above is for a sending unit spec'd out for the application you are using it for.
Hi, Thanks for the update. I agree with you. That is what you need on this style sending unit. As you know this will likely require playing around with a couple different OHM resisters to get the closest possible reading of accuracy. There is a possibility you could still have to mentally adjust the values between full and empty depending on your final selection.