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How can I troubleshoot my electric oil pressure gauge?

Most issues are due to incorrect wiring or sender hookup. The most common wiring issue is not having a good common ground between the gauge and sender. A common indicator of not having good wiring on your sender is the pointer on the Comp II LED oil pressure gauge going all the way to the right (open circuit on signal wire).

Check the Gauge with 0 Ohm Signal (Ground)
Connect the signal from the gauge to the gauge ground wire. This puts a signal of 0 ohms to the gauge. A Comp II LED gauge with 9200 sender will go to 0 PSI. A current SCX gauge with 9205 sender will go to 100 PSI.

Confirm the Gauge is OK by Using a Known Good Signal
Use a 47 ohm or 100 ohm resistor to verify the gauge with a known good signal other than 0 ohm (ground):

  • Install one end of the resistor to the gauge signal input and the other end to the gauge ground.
With power to the gauge and a resistor across the signal input and ground you will see the pointer move to to the corresponding dial position.
  • For gauges with 9200 sender: 47 ohms is approx 40 PSI, 100 ohms is approx 80 PSI.
  • For gauges with 9205 sender: 47 ohms is approx 90 PSI, 100 ohms is approx 70 PSI.
If you do not have access to a resistor but do have another working fuel level or temp gauge you can use the power, ground and signal connections from the known good gauge on the oil pressure gauge to verify that the oil pressure gauge is OK. Note, the pointer will move according to the ohm output from the sender you are using to test the gauge.

Confirm the Type of Sending Unit You Have
There are three types of oil pressure sending units. Confirm which sender you have and make sure that it is putting out a good signal and that it has a common ground with the gauge. We recommend grounding the gauge and sender together to eliminate any potential issues with not having a good common ground.

  • Type 2 is the most common sender (Our part 9200). It has a yellow label stating "WK = Ground". This type of sender is supplied with Comp II gauges and SCX gauges shipped after May 1, 2022.
  • Type 3 (our part 9205) is silver in color and has a white label stating "240-33 OHM (0-100 PSI)". This sender was supplied with most SCX gauges shipped 2015 through May 2021.
  • Type 1 has no label. This sender was supplied with most SCX gauges shipped before 2015. This sender does not have a ground terminal. The sender is grounded through the body of the sender.

Verify Wiring and Common Ground
Verify your wiring is good and that the gauge and sender both have a good common ground. We recommend grounding the gauge and sender together to eliminate any potential issues with not having a good common ground.

If you have a Type 1 sender (no label) make sure you have not connected anything to the WK terminal. Verify the sending unit has a good ground connection on the body of the sender. If in doubt, install a metal clamp around the sender body and run a wire from the clamp to a good ground location on the vehicle chassis.

Verify Ohm Signal from Sending Unit
Turn your vehicle on and let it idle. Disconnect the gauge signal wire from the sender and check the ohms output with a multi-meter as follows:

  • For 9200 sender, the G terminal is the signal and the WK terminal is the ground.
  • For 9205 sender, - terminal is the ground and S terminal is the signal.
  • For old Type 1 sender, the G terminal is the signal and the body of the sender is ground.

Check the SCX or Comp II pressure/ohm data (found here) and confirm that the sender ohm output is reading as expected.

Verify Ohm Signal at the Gauge
Reconnect the gauge signal wire to your sender, disconnect the signal wire from the gauge and check the ohms between the signal wire and gauge ground wire (signal wire needs to be disconnected from the gauge). The ohm reading should be the same as you measured at the sender. If it is not, then you will need to check your wiring (verify common ground etc.).

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