How to Troubleshoot VDO Sending Unitsby Quinten Plummer
VDO produces a third-party line of automotive gauges, ranging from temperature gauges to pressure gauges. VDO sending units monitor your automobile's components and processes and then report this information to your automobile's gauges. If you start to notice odd readings on your gauges, your automobile's components may not be at fault -- there may be a problem with your VDO senders.
Test a VDO temperature sender using a multimeter. Switch the multimeter to "Ohms." Touch the temperature sender with the multimeter positive lead, or clamp the positive lead to the sender. Touch or clamp the multimeter black lead to a solid metal portion of your car. The temperature sender should register 700 Ohms when cold and 22 Ohms after the car has warmed up.
Test the Ohm output of a VDO pressure sender using a multimeter. -- Set the multimeter to "Ohms." Touch or clamp the multimeter black lead to a solid metal portion of the car. Touch the sender with the multimeter positive lead. The sender should register 10 Ohms with the engine off. Start the engine and test the pressure sender again. For engines with 40 psi oil pumps, the sender should register 105 Ohms. It should register 152 Ohms for engines with 60 psi oil pumps.
Test your VDO fuel sender with a multimeter. Disconnect the fuel sender positive wire from the fuel gauge; disconnect the negative wire. Touch the negative lead of the multimeter to the negative wire and the positive lead to the positive wire. The fuel sender should show between 10 and 180 Ohms, depending on how much fuel is in the tank. It should register 10 Ohms on a full tank and 180 Ohms on a full tank. If your fuel level falls between full and empty, the Ohm output should register between 10 and 180 Ohms.
Test your VDO speed sender, also known as the "Hall Effect" sender. Disconnect the red and black wires, attached to terminals two and three, from the back of the speedometer. Switch a multimeter to "Volts," and then match the red and black leads of your multimeter to the red and black wires you have disconnected. The sender voltage should fall between five and 12 volts. Ensure that the wires are connected to the proper terminals on the gauge terminal block and that no wires are crossed or touching. The red wire goes to terminal two and the black wire goes to terminal three. The white wires connect to terminals six and eight. The 12V wire connects to terminal four.