Urrea UD88 User's Manual And Warranty Information page 82

E N G L I S H
NOTE: use a thermocouple adapter whose materials match
the thermocouple you are using.
2. Wire Device (Thermistor) Tests
Thermistors are variable resistors that are sensitive
to temperature level changes. As the temperature
changes, the thermistor's resistance value changes.
Typical thermistor applications are: Engine Coolant
Temp. (ECT) sensor, Air Charge Temp. (ACT) sensor,
Manifold Air Temp. (MAT) sensor, Vane Air Temp (VAT)
sensor and Throttle Body Temp (TBT) sensor, etc.
A thermistor can be tested either by watching the
resistance change or by watching the voltage change,
using the analog pointer on the Meter.
To check resistance change:
- Set the rotary switch to resistance (Ω).
Connect:
- Black test probe to the negative (-) terminal of the
sensor.
- Red test probe to the positive (+) terminal of the
sensor.
The resistance reading should match the temperature
of the sensor.
82
NOTE: consult the manufacturer's specifications for the
temperature of the sensor.
Voltage Change Test
To measure voltage change:
- Connect jumper wires between the connector and
the sensor.
- Set the rotary switch to voltage (
Connect:
- Black test probe to the negative (-) circuit from the
sensor.
- Red test probe to the circuit coming from the power
source.
Set:
- RECORD (MAX-MIN-AVG) function on the meter.
Start the engine. The voltage should change as the
temperature change. The signal this thermistor
generates is sent to the vehicle computer for
processing. Refer to the manufacturer's specifications.
If the voltage change is not within the specifications,
check the sources of resistance: poor connectors,
connections, or breaks in the wiring.
3. Wire Device (Potentiometer) Tests
The potentiometer is a variable resistor. The signal
it generates is used by the vehicle computer to
determine position and direction of movement of a
device within the component. Typical potentiometer
applications are: Throttle Position Sensor (TPS),
).