July 31, 2024
The tests below can be performed with a handheld multimeter.
If there is no reading: Set your handheld multimeter to a low range (less than 5k ohm).
- Measure the resistance between the two VW wires (orange and white-and-orange). A normal reading should be about 300 ohms. If the reading is very high or infinite, the coil is probably burned out (typically from lightning damage). If the reading is very low, the cable is probably damaged.
- Measure the resistance between the temperature sensor wires (blue and white). Thermistors should read about 3000 ohms. RTDs should reading about 2000 ohms. If the reading is very high or infinite, the temperature device is burned out. If the reading is very low, the cable is probably damaged.
If the reading is unstable: Set your handheld multimeter to a high range (10 or 20 M ohm).
- Measure the resistance between a VW wire and a Temp wire. The reading should very high or infinite.
- Measure the resistance between any of the colored wires and the drain (shield) wire. The reading should be very high or infinite.
- Measure the resistance between the shield wires of two VW sensors. The reading should be very high or infinite. A lower reading indicates the presence of a ground loop. Check that each instrument is isolated from the others when it is read. This may require rewiring your multiplexer. Contact the factory for suggestions.
- Some other sources of trouble may be electrical noise from nearby power lines or motors. A over-ranged or shocked instrument may also exhibit these problems.