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Introduction
No Reading
Unstable Reading
VW Temperature Sensor, 2012/6/20
Perform the tests below to check the sensor and cable.
Set your handheld multimeter to a low-ohm range (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 damaged (or the cable is
severed). If the reading is very low, the cable may have been crushed
and a short has developed.
Measure the resistance between the RTD/Thermistor wires (blue and
white). Thermistors should read about 3000 ohms. RTDs should read
about 2000 ohms. If the reading is very high or infinite, the tempera-
ture device is damaged (or the cable is severed). If the reading is very
low, the cable may have been crushed and a short has developed.
Set your handheld multimeter to a high range (10 or 20 M ohm).
Measure the resistance between a VW wire and an RTD/Thermistor
wire. The reading should be infinite or out of range.
Measure the resistance between any of the colored wires and the
drain (shield) wire. The reading should be infinite or out of range.
Measure the resistance between the shield wires of two installed VW
sensors. Wires must be disconnected from data logger or terminal
box to make this test. The reading should be very high or infinite. A
lower reading indicates the presence of a ground loop.
Other sources of unstable readings are electrical noise from nearby
power lines, radio transmitters, or motors. Also, over ranged or
shocked instruments can exhibit this problem.
Diagnostics
7
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